    [From the U.S. Government Printing Office, www.gpo.gov]

                     Gulf of Me)dco OCS Region
                                                                                 MMS

                         Distribution and Abundance of Marine Mammals in the
                                North-Central and Western Gulf of Mexico:
                                             Draft Interim Report

                     Gulf of Me)dco Region                                                OCS Study
                                                                                          MMS

                         Distribution and Abundance of Marine Mammals in the
                        North-Central and Western Gulf of Mexico: Draft Interim
                                                           Report

                                                           Authors:

                      R. Davis, B. Wursig, W. Evans, G. Fargion, R. Benson, J. Norris, and T. Jefferson.

                                              Texas Institute of Oceanography
                                             Texas A&M University at Galveston
                                                    Galveston, TX 77553.

                                    G. Scott, L. Hansen, K. Mullin, N. May, and T. Leming.

                                             Southeast Fisheries Science Center
                                             National Marine Fisheries Service
                                                  75 Virginia Beach Drive
                                                      Miami, FL 33149.

                                                           B. Mate
                                           Hatefield Marine Reseach Laboratory
                                                  Oregon State University.

                                               Prepared under MMS Contract
                                                      14-35-0001-30619
                                         and under Interagency Agreement 16197

                                                              by

                                              Texas Institute of Oceanography
                                                   Texas A&M University

                                                             and

                                             Southeast Fisheries Science Center
                                             National Marine Fisheries Service

                      Pubfished by
                      U.S., Department of the Interior
                      Minerals Management Service
                      Gulf of Mexico OCS Regional Office
                      New Orleans, Louisiana                                               October 1993
                 co                                LIBRARY
                 '-4                              NOAA/CCEH
                 C=                           1990 HOBSON AVE.
                                             CHAS). SC 29408-2623

                                                       DISCLAIMER

                      This draft report has not been reviewed by the Minerals Management Service
                      nor has it been approved for publication. Approval, when given, does not
                      signify that the contents necessarily reflect the views and policies of the
                      Service, not does mention of trade names or commercial products constitute
                      endorsement or recommendation for use.

                                                 REPORT AVAILABILITY

                      Extra copies of this Report may be obtained from the Public Information Unit
                      (Mail Stop OPS-3-4) at the following address:

                                          U.S. Department of the Interior
                                          Minerals Management service
                                          Gulf of Mexico OCS Regional Office
                                          1201 Elmwood Park Boulevard
                                          New Orleans, Louisiana 70123-2394

                                          Attention:

                                          [Telephone Number: 504-736-2519]

                                                         CITATION

                      Suggested citation:

                      Davis, R., G. Scott, B. Wursig, W. Evans, G. Fargion, L. Hansen, R. Benson, K.
                      Mullin, N. May, T. Leming, B. Mate, J. Non-is and T. Jefferson. 1993. Distribution
                      and Abundance of Marine Mammals in the North-Central and Western Gulf of
                      Mexico: Interim Report. Prepared    by the Texas Institute of Oceanography and
                      the National Marine Fisheries Service. OCS Study/MMS             U.S. Dept. of the
                      Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Regional Office, New
                      Orleans, LA. xx pp.

                                                    ABOUT THE COVER

                      Cover artwork shows the study area along the continental slope in the Gulf of
                      Mexico from the Texas-Mexico border to the Alabama-Florida state line and
                      between the 100 m and 2000 m isobaths.

                                                                                                     v

                                                       ABSTRACT

                     The purpose of this study is to determine the seasonal and            geographic
                     distribution and movements of cetaceans in areas potentially affected by
                     future oil and gas activities along the continental slope in the north-central
                     and western Gulf of Mexico. The study is restricted to the area bounded by the
                     Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m
                     isobaths. In addition to conducting aerial and shipboard visual surveys, this
                     program (hereafter referred to as the GulfCet Program) has collected
                     hydrographic data in situ and by remote sensing to characterize the preferred
                     habitats of cetaceans in the study area. When the analysis is complete, we will
                     identify environmental variables which correlate with the seasonal
                     distribution of cetaceans. Finally, we have attempted to tag and track a limited
                     number of sperm whales using satellite telemetry.

                     The GulfCet Program is a 3.25 year project which commenced on October 1,
                     1991 and will finish on December 31, 1994. This interim report summarizes
                     project accomplishments and results for the first four aerial and six shipboard
                     surveys (TAMUG), two of the regularly scheduled Ichthyoplankton/ Marine
                     Mammal survey cruises conducted by the National Marine Fisheries Service,
                     and three sperm whale tagging cruises. When completed, this study will help
                     the MMS to assess the potential effects of deepwater exploration and
                     production on marine mammals in the Gulf of Mexico.

                                                                                                                                                   vii

                                                                        TABLE OF CONTENTS

                              Section

                              ABSTRACT       ..........................................................................................            v
                              LIST OF FIGURES         ........................................................................................................ @d
                              LIST OF TABLES         .........................................................................................................  xvii
                              ACKNOWLEDGEMENTS                 ............................................................................................... )dx

                              1. EXECUTIVE SUMMARY                 ...................................................................................1

                                   1.1 Overview        .......................................................................................................1
                                   1.2 Cetacean Surveys            ........................................................................................1

                                       1.2.1   Survey Organization and Objectives                  .................................................1
                                       1.2.2   Aerial Surveys        .......................................................................................1
                                       1.2.3   Shipboard Visual Surveys: TAMUG                    ....................................................2
                                       1.2.4   Shipboard Visual Surveys: NMFS                  .......................................................3
                                       1.2.5   Shipboard Acoustic Survey               .................................................................4
                                       1.2.6   Satellite Tagging of Sperm Whales                  ....................................................5

                                   1.3 Environmental Data Survey                  .......................................................................6

                                   1.3.1 Hydrographic Surveys: TAMUG                      ..............................................................7
                                   1.3.2 Remote Sensing and Geographic Information System                               ......................     8

                              II.  INTRODUCTION             ................................................................................................. 10

                                   2.1 Background and Objectives                  ........................................................................ 10
                                   2.2 Program Management and Personnel                        ..................................................... 10
                                   2.3 Report Organization              .................................................................................... 13

                              III. CETACEAN SURVEYS                .................................................................................... 16

                                   3.1 Introduction         .................................................................................................. 16
                                   3.2 Aerial Surveys          .............................................................................................. 16

                                       3.2.1 Methods        ................................................................................................... 16
                                       3.2.2 Results and Discussion               ......................................................................... 17

                                   3.3 Shipboard Visual Surveys                 .......................................................................... 26

                                       3.3.1 Visual Surveys: TAMUG                 ....................................................................... 26

                                           3.3.1.1 Methods         .......................................................................................... 26
                                           3.3.1.2 Results and Discussion              ................................................................. 28

                                       3.3.2 Visual Surveys: NMFS                ......................................................................... 31
                                           3.3.2.1 Methods         ................... :**"***"** ...* ...-...  **************"**""***"**,****,*******,**,* 31
                                           3.3.2.2 Results and Discussion              ................................................................. 32

                                       3.3.3 Acoustic Surveys: TAMUG                  ..................................................................... 47

                                                                                                                                                             viii

                                             3.3-3.1 Methods           .......................................................................................... 47
                                             3.3.3.2 Results and Discussion                   ................................................................. 53
                                             3.3.3.3 Summary             ........................................................................................ 57

                                     3.4   Satellite Tagging of Sperm Whales                       .........................................................  61

                                             3.4.1 Introduction            ........................: ............................................................ 61
                                             3.4.2 Methods          ............................................................................................. 61
                                             3.4.3 Results          .............................................................................................. 62
                                             3.4.4 Discussion            .....                                                                                70
                                             3.4.5 Recommendations                   ........................................................................... 70

                                     3.5   References for Section III              ........................................................................   71

                               IV.   ENVIRONMENTAL DATA SURVEYS                              .........................................................        73

                                     4.1 Introduction            ................................................................................................ 73

                                     4.2 Hydrographic Surveys: TAMUG                          ............................................................... 77

                                         4.2.1 Introduction            ........................................................................................ 77
                                         4.2.2 Transect and Cruise Design                      ............................................................... 77
                                         4.2.3 Summaries of Cruises 1- 6                     .................................................................. 77
                                         4.2.4 Shipboard Measurements and Procedures                                 .....................................    81

                                             4.2.4.1 CTD/Rosette Casts                 .......................................................................... 81
                                             4.2.4.2 XBT Deployments                   .......................................................................... 81
                                             4.2.4.3 MIDAS          ............................................................................................. 82

                                         4.2.5 Data Analysis             ........................................................................................ 82

                                             4.2.5.1 XBT and CTD Processing                      .............................................................. 82
                                             4.2.5.2 Multiple Interface Data Acquisition System(MIDAS)                                      ..........        83
                                             4.2.5.3 Dynamic Height                 ........................................................................... 83

                                         4.2.6 Technical Discussion                  .......................................................................... 83

                                             4.2.6.1 Characteteristic Temperature-Salinity Relationship                                   ...........         83
                                             4.2.6.2 20-C, 15-C, and 8'C Isotherms                        ................................................... 92
                                             4.2.6.3 Dynamic Height                  .......................................................................... 112
                                             4.2.6.4 Chlorophyll Data                 .......................................................................... 112
                                             4.2.6.5 Mississippi River: 1992 versus 1993                             ........................................ 112

                                         4.2.7 Conclusions             .......................................................................................... 132

                                     4.3 Remote Sensing and Geographic Information System                                      .......................        132

                                         4.3.1 Introduction            ......................................................................................... 132

                                         4.3.2 Tasks Completed                 ................................................................................... 132

                                             4.3.2.1 Support for Ship and Aerial Surveys                            ......................................... 132

                                                                                                                                                   ix

                                          4.3.2.2 Support for the Sperm Whale Tagging cruises                          ........................  137
                                          4.3.2.3 GIS Procurement              ............................................................................ 137
                                          4.3.2.4 Acquisition of Collateral Data Sets                   .............................................. 137
                                          4.2.2.5 Infrastructure Improvements                   .................................................... 137

                                      4.3.3 GIS Data Management and Analysis                       ................................................... 138

                                          4.3.3.1 Base Map Coordinate System                    ........................................................ 138
                                          4.3.3.2 Raster versus Vector Data Models                     ............................................... 138
                                          4.3.3.3 Processing Protocol              ....................................................................... 139

                                  4.4    References for Section IV           ........................................................................... 140

                                                                           LIST OF FIGURES

                              Figure no.                    Caption

                              2.1                           Study area between the 100 and 2000 m isobaths,
                                                            extending as far east as the Florida-Alabama
                                                            border, and as far southwest as Texas-Mexico border                           ....    12

                              3.1                           Location of each marine mammal group sighted (+)
                                                            during Summer 1992 GulfCet Aerial Survey                        ..................... 19

                              3.2                           Location of each marine mammal group sighted (+)
                                                            during Fall 1992 GulfCet Aerial Survey                   ............................. 21

                              3.3                           Location of each marine mammal group sighted (+)
                                                            during Winter 1993 GulfCet Aerial Survey                     .......................  22

                              3.4                           Location of each marine mammal group sighted (+)
                                                            during Spring 1993 GulfCet Aerial Survey                     ........................ 23

                              3.5                           Location (+) of leatherback sea turtles sightings
                                                            during Summer and Fall 1992, Winter and Spring
                                                            1993 GulfCet Aerial Surveys              ................................................ 24

                              3.6                           On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 1 of spring-
                                                            summer survey, NOAA ship                 .................................................. 33

                              3.7                           On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 2 of spring-
                                                            summer survey, NOAA ship                 .................................................. 34

                              3.8                           On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 3 of spring-
                                                            summer survey, NOAA ship                 .................................................. 35

                              3.9                           On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 1 of winter survey
                                                            summer survey, NOAA ship                 .................................................. 36

                              3.10                          On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 2 of winter survey
                                                            summer survey, NOAA ship                 .................................................. 37

                              3.11                          On-effort daylight cruise track and location (+) of
                                                            cetacean sightings during Leg 3 of winter survey
                                                            summer survey, NOAA ship                 ................................................. 38

                              3.12                          Locations (+) of all cetacean groups sighted during
                                                            SEFC marine mammal cruises in the northern Gulf of
                                                            Mexico: 1990- 1992           ................................................................. 41

                                                                                                                                                  )di

                                                                           LIST OF FIGURES

                             Figure no.                     Caption

                             3.13                           Locations (+) of S. attenuata groups sighted
                                                            during SEFC marine mammal cruises in the
                                                            northern Gulf of Me@dco: 1990- 1992                  ................................. 42

                             3.14                           Locations (+) of S. frontalis groups sighted
                                                            during SEFC marine mammal cruises in the
                                                            northern Gulf of Me)dco: 1990- 1992                  .................................. 43

                             3.15                           Locations (+) of Tursiops truncatus groups sighted
                                                            during SEFC marine mammal cruises in the
                                                            northern Gulf of Me)dco: 1990- 1992                  .................................. 44

                             3.16                           Locations (+) of Grampus gilseus groups sighted
                                                            during SEFC marine mammal cruises in the
                                                            northern Gulf of Me)dco: 1990- 1992                  .................................. 45

                             3.17                           Locations W of Physeter macrocephalus groups
                                                            sighted during SEFC marine mammal cruises in
                                                            the northern Gulf of Me@dco: 1990- 1992                     ........................... 46

                             3.18                           Schematic diagram of the hydrophone array                        ..................   48

                             3.19                           Blowup schematic diagram of the low frequency
                                                            section of the hydrophone array                 ........................................ 49

                             3.20                           The directivity pattern of the hydrophone array                        ...........    so

                             3.21                           The configuration of the on-board electronics                      ...............    51

                             3.22                           Distribution of acoustic contacts on Cruise 1                    .................... 54

                             3.23                           Distribution of acoustic contacts on Cruise 2                    .................... 55

                             3.24                           Distribution of acoustic contacts on Cruise 3                    .................... 56

                             3.25                           Distribution of Sperm whales on Cruises 1- 3                     ...................  58

                             3.26                           Distribution of Tursiops truncatus (circles) and
                                                            Stenella attenuata (squares) during Cruises 1-3                       ............    59

                             3.27                           Sperm whale sightings, June 6-29, 1993 aboard R/V
                                                            Acadiana     .................................................................................. 65

                             3.28                           R/V Acadiana cruise track and sperm whale
                                                            sightings June 23-24, 1993 with seismic activity
                                                            begininng      ............................................................................... 66

                                                                                                                                                 )dii

                                                                           11ST OF FIGURES

                              Figure no.                    Caption                                                                          EM

                              3.29                          R/V Acadiana cruise trackand sperm whale
                                                            sightings June 25-29, 1993 with activity seismic
                                                            vessel   ........................................................................................ 67

                              4.1                           Mississippi River flow from 1932 -1986                     ............................ 74

                              4.2                           Time series 1979 -1986 of Mississippi River flow
                                                            & chlorophyll pigment data from CZCS (data in
                                                            close proNimity to GulfCet station 11-106)                   ......................... 75

                              4.3                           Time series 1979 -1986 of Mississippi River flow
                                                            & chlorophyll pigment data from CZCS (data in
                                                            close pro)dmity to GulfCet station 12-125)                   ......................... 76

                              4.4                           GulfCet station plan          ............................................................... 78

                              4.5                           Total number of CTD & XBT stations Cruises 1-6                        ................ 80

                              4.6                           T-S Plot: all CTD data Cruises 2-6               .......................................... 84

                              4.7                           Winter T-S Plot: CTD data Cruise 4                 ....................................... 85

                              4.8                           Spring T-S Plot: CTD data Cruises 1 & 5                    ............................... 86

                              4.9                           Summer T-S Plot: CTD data Cruises 2 & 6                      ............................. 87

                              4.10                          Fall T-S Plot: CTD data Cruise 3               .............................................. 88

                              4.11                          T-10 XBT Temperature Plot: Cruises 1- 6                    ............................. 89

                              4.12                          T-7 XBT Temperature Plot: Cruises 1- 6                     ............................... 90

                              4.13                          T-20 XBT Temperature Plot: Cruises 1- 6                    ............................. 91

                              4.14                          Topography of the 8*C temperature surface
                                                            based on all XBT and CTD data Cruise 1                     ................................ 93

                              4.15                          Topography of the I 5'C temperature surface
                                                            based on all XBT and CTD data Cruise 1                     ................................ 94

                              4.16                          Topography of the 20'C temperature surface
                                                            based on all XBT and CTD data Cruise 1                     ................................ 95

                              4.17                          Topography of the 8'C temperature surface
                                                            based on all XBT and CTD data Cruise 2                     ................................ 96

                              4.18                          Topography of the 15'C temperature surface
                                                            based on all XBT and CTD data Cruise 2                     ................................ 97

                                                                                                                                                 )dv

                                                                       IIST OF FIGURES

                             Figure no,                    Caption                                                                         RM

                             4.19                          Topography of the 20*C temperature surface
                                                           based on all XBT and CTD data Cruise 2                    ................................ 98

                             4.20                          Topography of the 8'C temperature surface
                                                           based on all XBT and CTD data Cruise 3                    ................................ 99

                             4.21                          Topography of the 15'C temperature surface
                             4.22                          based on all XBT and CTD data Cruise 3                    ................................ 100
                                                           Topography of the 20'C temperature surface
                                                           based on all XBT and CTD data Cruise 3                    ................................ 101

                             4.23                          Topography of the 8'C temperature surface
                                                           based on all XBT and CTD data Cruise 4                    ................................ 102

                             4.24                          Topography of the 15'C temperature surface
                                                           based on all XBT and CTD data Cruise 4                    ................................ 103

                             4.25                          Topography of the 20'C temperature surface
                                                           based on all XBT and CTD data Cruise 4                    ................................ 104

                             4.26                          NOAA-AVHRR SST (*C) analysis in the western Gulf
                                                           of Me)dco for February 12, 1993
                                                           (Coastal Studies Institute)          ...................................................... 105

                             4.27                          Topography of the 8'C temperature surface
                                                           based on all XBT and CTD data Cruise 5                    ................................ 106

                             4.28                          Topography of the 1 50C temperature surface
                                                           based on all XBT and CTD data Cruise 5                    ................................ 107

                             4.29                          Topography of the 200C temperature surface
                                                           based on all XBT and CTD data Cruise 5                    ................................ 108

                             4.30                          Topography of the 8*C temperature surface
                                                           based on all XBT and CTD data Cruise 6                    ................................ 109

                             4.31                          Topograpy of the 15*C temperature surface
                                                           based on all XBT and CTD data Cruise 6                    ................................ 110

                             4.32                          Topography of the 20'C temperature surface
                                                           based on all XBT and CTD data Cruise 6                    ................................ 111

                             4.33                          Surface dynamic topography (cm) with
                             4.34                          respect to 800m from GulfCet 1 survey                     .............................. 113
                                                           Surface dynamic topography (cm) with
                                                           respect to 800m from Gu1fCet 2 survey                     .............................. 114

                                                                                                                                                  xv

                                                                        IIST OF FIGURES

                              Fizure no.                    Captio                                                                          EM

                              4.35                          Cruise 2 surface dynamic topography (cm)
                                                            and 1ATEX-A drifter # 2447, August 1992                      .......................... 115

                              4.36                          Surface dynamic topography (cm) with
                                                            respect to 800m from GulfCet 3 survey                   .............................. 116

                              4.37                          Surface dynamic topography (cm.) with
                                                            respect to 800m from GulfCet 4 survey                   .............................. 117

                              4.38                          Cruise 3 surface dynamic topography (cm.)
                                                            and LATEX-A drifter # 2447, November 1992                         .................... 118

                              4.39                          Surface dynamic topography (cm) with
                                                            respect to 800m from GulfCet 5 survey                   ............................... 119

                              4.40                          Surface dynamic topography (cm) with
                                                            respect to 800m from GulfCet 6 survey                   .............................. 120

                              4.41                          Chlorophyll a surface distribution in mg/m3
                                                            during the November 1992 survey (Cruise 3)                        ..................  121

                              4.42                          Chlorophylla surface distribution in mg/m3
                                                            during the February 1992 survey (Cruise 4)                      ....................  122
                              4.43                          Chlorophyll a surface distribution in mg/m3
                                                            during the May 1993 survey (Cruise 5)                   ............................. 123
                              4.44                          Chlorophyll -q surface distribution in mg/m3
                                                            during the August 1993 survey (Cruise 6)                     ........................ 124

                              4.45                          Salinity distribution at 0 rn during the August 1992
                                                            survey (Cruise 2)        .................................................................... 125

                              4.46                          Salinity distribution at 3 rn during the August 1992
                                                            survey (Cruise 2)        .................................................................... 126

                              4.47                          Salinity distribution at 5 rn during the August 1992
                                                            survey (Cruise 2)        .................................................................... 127

                              4.48                          Salinity distribution at 0 rn during the August 1993
                                                            survey (Cruise 6)        .................................................................... 128

                              4.49                          Salinity distribution at 3 rn during the August 1993
                                                            survey (Cruise 6)        .................................................................... 129

                              4.50                          Salinity distribution at 5 rn during the August 1993
                                                            survey (Cruise 6)        .................................................................... 130

                                                                                                xvi

                                                IIST OF FIGURES

                    Figure no.          Caption

                    4.51                N0AA-AVHRR reflectance analysis-in the
                                        western Gulf of Me@dco for August 10, 1993
                                        (Coastal Studies Institute) ..................................................... 131

                    4.52                NOAA-AVHRR SST analysis in the Gulf of Me)dco,
                                        April 11, 1993 .......................................................................... 133

                                                                                                                                                 xvii

                                                                            LIST OF TABLES

                              Table no,                     Caption                                                                          EM

                              2.1                           Cetaceans of the Gulf of Me)dco               ........................................... 11

                              2.2                           Management structure, principal investigators
                                                            and their affiliations         ............................................................. 15

                              3.1                           Summary of Summer 1992, Fall 1992, Winter 1993,
                                                            and Spring 1993 GulfCet Aerial Surveys                     ............................ 18

                              3.2                           Species of cetaceans sighted, mean group sizes,
                                                            and mean water depths from the Summer 1992,
                                                            Fall 1992, Winter 1993, and Spring 1993 GulfCet
                                                            Aerial Surveys        ........................................................................ 25

                              3.3                           Summary of hours and kilometers of survey
                                                            effort conducted (10 refers to independent
                                                            observers effort)        ................................................................... 29

                              3.4                           Summary of marine mammal sightings: TAMUG                            ............     30

                              3.5                           Summary of cetacean sightings from the
                                                            spring-summer and winter vessel survey (NMFS)                          ........       39

                              3.6                           Average water depths for selected acoustic contacts                        .....      60

                              3.7                           Sperm whale sightings, June 7-29, 1993                     ........................... 68

                              3.8                           Other marine mammal species sighted June
                                                            7-29, 1993      ................................................................................. 69

                              4.1                           Date and time (GMT) of acquisition, satellite and
                                                            orbit numbers of the 106 AVHRR images acquired
                                                            through October 1986              .......................................................... 134-5

                              4.2                           GIS data base characteristic for the map layers
                                                            identified for the GulfCet project               ...................................... 136

                                                                                                  Nix

                                                ACKNOWLEDGEMENTS

                     Many persons contributed to the completion of this phase of the study
                     including the crews and graduate students who worked on the research vessels
                     and aircraft, laboratory technicians, and the data management staff. We would
                     like to recognize the efforts of Stefan Brager, David Brandon, Elisif Brandon,
                     Ronnie Carroll, Gina Childress, Shane Collier, Lisa de los Santos, Mike Duncan,
                     Theodore Engelhardt, Lesley Higgins, Wayne Hoggard, Mary Howley, Shane
                     Kanatous, Don Ljungblad, Spencer Lynn, Mary Lou Mate, Luis Montano,
                     Patricia Mumford, Sharon Nieukirk, Sean O'Sullivan, Dwight Peake, Kevin
                     Rademacher, Logan Respess, Carol Roden, Andy Schiro, Cheryl Schroeder, Troy
                     Sparks, Kate Stafford, and Dave Weller. We would like to thank Robert Avent
                     (Contracting Officer's Technical Representative) for his direction and advice,
                     and the Scientific Review Board (SRB) for their thoughtfull review and
                     comments on goals and results of this project.

                     We gratefully thank the Texas Institute of Oceanography and the National
                     Marine Fisheries Service for cost-sharing the use of all research vessels used
                     for the surveys and sperm whale tagging on this project.

                                               L Executive Summary

                    1.1 Overview

                    The MMS has the responsibility to assure that oil and gas operations on the
                    Outer Continental Shelf (OCS) Leases in the Gulf of Mexico are conducted in a
                    manner that reduces risks to the marine environment. To meet their
                    responsibilities under the Marine Mammal Protection Act (MMPA) of 1972 and
                    the Endangered Species Act (ESA) of 1973, the MMS must understand the effects
                    of oil and gas operations on marine mammals.

                    The purpose of this study is to determine the seasonal and geographic
                    distribution and movements of cetaceans in areas potentially affected by
                    future oil and gas activities along the continental slope in the north-central
                    and western Gulf of Mexico. The study is restricted to the area bounded by the
                    Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m
                    isobaths. In addition to conducting aerial and shipboard visual surveys, the
                    GulfCet Program has collected hydrographic data in situ and by remote
                    sensing to characterize the preferred habitats of cetaceans in the study area.
                    When the analysis is complete, we will identify environmental variables
                    which correlate with the seasonal distribution of cetaceans. Finally, we have
                    attempted to tag and track a limited number of sperm whales using satellite
                    telemetry.

                    The GulfCet Program is a 3.25 year project which commenced on October 1,
                    1991 and will finish on December 31, 1994. Because the final surveys will not
                    be completed until April 1994, this report does not include models of cetacean
                    abundance or extensive correlations of cetacean distribution with
                    environmental variables. Instead, this interim report summarizes project
                    accomplishments and results for the first four aerial and six shipboard
                    surveys, two of the regularly scheduled Ich thyopl ank ton/ Marine Mammal
                    survey cruises conducted by the National Marine Fisheries Service, and three
                    sperm whale tagging cruises.

                    The GulfCet Program is being conducted by the Texas Institute of
                    Oceanography, National Marine Fisheries Service at the Southeast Fisheries
                    Science Center, and Oregon State University.

                    1.2 CCtacean Surveys

                    1.2.1 Survey Organization and Objectives

                    A major part of the GulfCet Program's field research consists of seasonal, line
                    transect surveys to determine the distribution and to estimate the abundance
                    of cetaceans in the study area. Three types of surveys are being conducted: 1)
                    visual surveys from an aircraft, 2) visual surveys from a ship, and 3) acoustic
                    surveys using a linear hydrophone array towed behind the visual survey ship.

                    1.2.2 Aerial Survg_ys

                     Four seasonal aerial surveys were completed for the summer (10 August-19
                    September 1992), fall (3 November-16 December 1992), winter (1 February-22

                                                                                                      2

                     March 1993), and spring (25 April-1 June 1993) seasons. The objective of the
                     surveys was to collect seasonal line transect and distributional data on
                     cetaceans.

                     The study was designed to survey about 6,500 transect km per season. Transects;
                     were oriented perpendicular to the bathymetry. Surveys were conducted using
                     standard cetacean aerial survey methods. Transect lines were surveyed from
                     7 5 0 feet at a speed of 110 knots.

                     A total of 164 cetacean groups was sighted on-effort during the four surveys.
                     Twenty-five sightings were off-effort including a group of ten killer whales.
                     At least 18 species of cetaceans have been sighted to date. Bottlenose dolphins,
                     pantropical spotted dolphins, dwarf/pygmy sperm whales, Risso's dolphin
                     were the most commonly sighted species.On-effort group sighting rates were
                     highest in summer and spring, and lowest in fall. The summer, winter and
                     spring average group sizes of all cetacean groups sighted were over twice the
                     fall average. Of species sighted more than once, pantropical spotted dolphins
                     had the largest average group size of all the species sighted, whereas
                     dwarf/pygmy sperm whales had the smallest. Only three groups of pantropical
                     spotted dolphins were sighted in winter. However, a group of 150 striped
                     dolphins and a group of 200 spinner dolphins were seen in winter. These two
                     groups accounted for 38% of the cetaceans sighted in winter. During the
                     spring, groups of 175 and 400 melon-headed whales were sighted. These groups
                     accounted for 50% of the animals sighted in spring.

                     With sightings from all four seasons combined, cetacean groups were sighted
                     throughout the length of study area and at all water depths. However, distinct
                     species were found at different water depths. Bottlenose dolphins and Atlantic
                     spotted dolphins were sighted primarily near the shelf edge (200-300 m).
                     Pantropical spotted dolphins and dwarf/pygmy sperm whales were found in
                     much deeper water (greater than 300 m). Pilot whales and Risso's dolphins
                     inhabited the greatest range of water depths (greater than 1500 m).

                     1.2.3 Shipboard Visual Surveys (TAMUG)

                     The study area was surveyed along 14 north-south transect lines. Survey
                     procedures followed closely those developed for dolphin surveys in the eastern
                     tropical Pacific. Two members of each survey teams searched for marine
                     mammals through pedestal-mounted 25X150 Fujinon binoculars, while the
                     third observer acted as data recorder and assisted in searching with 7X
                     binoculars. Sighting effort was conducted during daylight hours in which
                     sighting conditions were acceptable (Beaufort sea states of less than 6 with
                     good visibility).

                     A total of 340.81 hours of sighting effort was conducted on the first six cruises.
                     This represents 4587.49 kilometers of transect line surveyed. A total of 258
                     marine mammal sightings were made within the study area on the first six
                     cruises. Of these, 182 were "on effort" and are usable in the density and
                     abundance estimates. The 76 "off-effort" sightings can be used only in
                     estimating mean herd size, and will not be used to estimate density and
                     abundance.

                                                                                                     3

                     Based only on the sightings from these six cruises, the only species with an
                     adequate sample size for abundance estimates is the bottlenose dolphin (32 on
                     effort sightings). It is likely that the number of sperm whale sightings will
                     equal at least 30 by the end of the project. All other species will have to be
                     pooled based on the number of sightings, taxonomic relationships, and general
                     habitat types.

                     Sperm whales and pantropical spotted dolphins were the most common
                     cetaceans seen in oceanic waters. An unexpected finding was the paucity of
                     short-finned pilot whales. Several poorly-known species have turned out to be
                     moderately common (beaked whales, pygmy and dwarf sperm whales, melon-
                     headed whale, and Fraser's and clymene dolphins). Both melon-headed whales
                     and Fraser's dolphins were almost completely unknown in the Gulf of Mexico
                     before this study began, each represented by one or two standings. The first
                     live sightings of these species in the Gulf (and for Fraser's dolphin, the first
                     for the entire Atlantic Ocean) were recorded during this project. The clymene
                     dolphin was well-known in the Gulf from strandings previous to this project,
                     but also was poorly-represented by live sightings.

                     1.2.4 Shipboard Visual Surveys (NMFS)

                      The Southeast Fisheries Science Center (SEFSQ has conducted two of four
                     planned vessel surveys aboard the NOAA RV Oregon II as part of the SEFSC
                     contributed effort to the Gulfcet Program. The first survey was conducted from
                     April 21-June 8, 1992 (spring-summer), and the second survey took place
                     during January 4-February 14, 1993 (winter). Both surveys were designed to
                     collect: 1) marine mammal sighting data to estimate abundance, distribution
                     and diversity, and 2) environmental data to evaluate factors which may affect
                     the distribution, abundance and diversity of marine mammals.

                     Visual sighting data were collected by two teams of three observers during
                     daylight hours, weather permitting (Le, no rain, Beaufort sea state less than
                     6). Two observers searched for marine mammals using high-power (25 power)
                     binoculars mounted on the ship's flying bridge. The third observer
                     maintained a search of the area near the trackline unaided and with handheld
                     binoculars, and recorded data.

                     A total of 6,154 transect kilometers were visually sampled for marine mammals
                     during the spring-summer survey resulting in 273 sightings of at least 20
                     species of cetaceans. The bottlenose dolphin and the pan-tropical spotted
                     dolphin were the most frequently sighted species and accounted for 21% and
                     19%, respectively, of identified sightings. Risso's dolphins, sperm whales, and
                     dwarf sperm whales were the next most frequently sighted, and accounted for
                     11 V6, 8%, and 8%, respectively, of identified sightings.

                     The winter survey resulted in the visual sampling of 4,017 transect kilometers.
                     At least 10 cetacean species were observed in a total of 46 sightings. Sperm
                     whales were the most commonly sighted cetaceans, with 9 sightings (25% of
                     identified sightings).Atlantic spotted dolphins and pan-tropical spotted
                     dolphins were the next most common with six herd sightings each (17% each
                     of identified sightings).

                                                                                                    4

                    The Stenefla dolphins, with the exception of the Atlantic spotted dolphin, were
                    sighted most frequently in the deeper, off-shelf waters of the survey area.
                    Sightings of bottlenose dolphins, Risso's dolphins, and Atlantic spotted
                    dolphins all appeared to occur quite frequently along the edge of the
                    continental shelf. However, whereas Atlantic spotted dolphins were sighted
                    only along the shelf edge, bottlenose dolphins were also seen frequently on
                    the continental shelf while Risso's dolphins were also seen in the deeper Gulf
                    waters.

                    Members of the sperm whale family were sighted both along the shelf edge
                    and in the deeper waters of the survey area. Kogia sp. sightings were located
                    throughout the deeper waters, with no apparent pattern. Sightings of sperm
                    whales, however, showed an apparent disjunct distribution with sightings in
                    Mississippi and DeSoto canyons and a band along the southern edge of the
                    survey area.

                    Four species not seen on the previous SEFSC marine mammal vessel surveys
                    were observed on the present surveys. Blainville's beaked whale,the melon-
                    headed whale, and Fraser's dolphin were all sighted on the spring-summer
                    survey, and melon-headed whales were seen on the winter survey. These
                    observations represented some the first documented sightings of these species
                    in the Gulf of Mexico (Fraser's dolphins were observed earlier in 1992 during a
                    Texas A&M shipboard visual and acoustic survey). Melon-headed whales were
                    also observed during the winter survey, and the first SEFSC vessel sightings of
                    killer whales occurred during the spring-summer survey.

                    1.2.5 Shil2boa[d Acoustic Surveys

                    A linear hydrophone array was towed behind the Texas A&M University visual
                    survey ship to record the distinctive underwater vocalizations of cetaceans.
                    This passive acoustic survey technique enabled us to identify cetaceans in the
                    vicinity of the ship in order to determine their distribution and to estimate
                    their abundance. The towed array has 195 hydrophones and an overall
                    frequency sensitivity from 10  Hz to 30 kHz, with maximum sensitivities at 30
                    Hz, 480 Hz, 3.84 kHz, 5 kHz, 10 kHz, and 15 kHz. The array has maximum
                    sensitivity in a ringed pattern perpendicular to the long axis of the array and
                    very little sensitivity either  fore or aft. It therefore detects little ship-
                    generated noise, particularly the higher frequencies.

                    The towed array was deployed whenever the ship was on a transect line.It was
                    towed at a uniform speed of 5 knots for the first four cruises and 6.5 knots for
                    cruises five and six. The speed of the vessel determines the depth of the array,
                    with an approximate depth of 18 m at a speed of 5 knots and 12 m at 6.5 knots.

                    A complete list of contacts which includes the species, date and location of
                    each acoustic contact is included in the Appendix. It is important to note that
                    the locations shown for marine mammals are for "first contact", which may
                    not be the final, computed location for these contacts. This is a problem
                    primarily for sperm whales which can be heard over 20 miles from the vessel.

                    A total of 4,496 miles (96% of the planned distance) was acoustically surveyed
                    during Cruises 1-4. The 4% which was not survey resulted from equipment
                    failure or poor weather. We had a total of 246 acoustic contacts on 9 10 recorded

                                                                                                     5

                     tapes. This is equivalent to 0.0547 acoustic contacts/survey mile. Many of these
                     contacts represent more than one animal.

                     The most common marine mammal acoustic contacts (149) have been
                     unidentified dolphins. These contacts were generally whistles recorded
                     primarily at night or during poor weather conditions when visual
                     identification was impossible. Of the 64 identified marine mammal acoustic
                     contacts, 3 3 (5 1 %) have been from sperm whales.

                     The majority of the sperm whale contacts have been off the mouth of the
                     Mississippi River or on the western side of the study area. Contacts with
                     bottlenose dolphins have occurred along the shallower, northem edge of the
                     study area, whereas contacts with pan-tropical spotted dolphins have been in
                     the deeper water along the eastem continental slope.

                     These distribution patterns are reflected in the average water depths for
                     acoustic contacts. Pan-tropical spotted dolphins and sperm whales were found
                     in the deepest water (mean depths = 1667 m and 1272 m, respectively) while
                     bottlenose dolphins occurred in more shallower water (mean depth = 315 m).
                     Several of the deeper bottlenose dolphin contacts occurred off the mouth of
                     the Mississippi River, where the continental shelf is narrow (i.e. 10 miles).

                     1.2.6 Satellite Tagging of Sperm Whales

                     Oregon State University was responsible for placing Satellite-linked Time-
                     Depth Recorders (SLTDRs) on sperm whales to determine their movements,
                     diving behavior and preferred habitat. To accomplish this goal, three cruises
                     were undertaken: two in the Gulf of Mexico (October 1992 and June 1993) and
                     one in the Galapagos (March 1993). The Galapagos cruise was intended as a test
                     for tag deployment and attachment.

                     The SLTDRs used for this project were designed and built by Oregon State
                     University using Wildlife Computers TM controller boards and Telonics TM ST-6
                     Platfonn Transmitter Terminals (PTTs) and housed in a stainless steel cylinder
                     (0.05 rn diameter, 0.19 m long, 0.8 kg in weight). The exterior of the housing
                     had attachments which consisted of two stainless steel rods (0.127 m long, 0.006
                     m diameter) with one pair of folding toggles mounted behind double-edged
                     blades at the end of each rod.

                     The transmitters were attached to whales with compound crossbow capable of
                     generating 150 lbs.of force. The SLTDR was attached to an aluminum shaft with
                     a "C"-shaped cup at one end. The shaft with the SLTDR was then fired from the
                     crossbow. A line (20 lbs. test) attached to the aluminum shaft enabled the
                     SLTDR to be recovered should it miss the whale. Once the SLTDR was attached to
                     the whale, the shaft was designed to fall off.
                     The SLTDRs collected data over eight, three-hour summary periods daily.
                     These data included three histograms: maximum depth of all dives, duration of
                     dive, and time spent at various depth ranges. Other data for each three hour
                     period included the longest dive, deepest dive, duration of deepest dive,
                     temperature at deepest depth, longest surface duration uninterrupted by a
                     submergence of greater than 6 seconds, and total surface duration.

                                                                                                  6

                    The first tagging cruise was conducted from September 30 to October 14, 1992
                    in the Gulf of Mexico. The cruise covered an area where previous GULFCET
                    cruises and aerial surveys had observed sperm whales, but had to remain
                    within the ship's operational limits (offshore to 100 miles from Venice, LA).
                    Visual contact with 8-10 sperm whales was made only once for about four
                    hours on October 9. Unfortunately, we did not get close enough to tag any
                    animals.

                    The second cruise was conducted in the eastern Pacific off the Galapagos
                    Islands from 20-31 March, 1993. The purpose of this cruise was to test
                    techniques to approach and attach SLTDRs to sperm whales.The waters around
                    the Galapagos were an ideal test ground because, unlike the Gulf of Mexico, the
                    seasonality and distribution of large numbers of sperm whales had been well
                    documented for this area.On March 26, we succeeded in attaching a SLTDR to a
                    sperm whale, but the telemeter failed to transmit data. Two other tagging
                    attempts were unsuccessful.

                    The third tagging cruise was conducted 6-29 if June 1993 in the Gulf of Mexico.
                    The vessel covered 2331.4 km searching for sperm whales. A maximum of 87
                    individuals were seen during the cruise.The sperm whales we found were
                    quite small. Most were less than 8 m in length and were considered too small to
                    tag; a few were up to 8 m. Two animals were tagged; the first (about 8 rn in
                    length) on 7 June and the second (about 7 m in length) on 11 June. None of the
                    telerneters transmitted data.

                    While searching for sperm whales in the Gulf of Mexico, we obtained some
                    circumstantial evidence that active seismic vessels may affect the distribution
                    of sperm whales. Although our observations represent circumstantial
                    evidence, the change in whale sightings after the onset of seismic activity is
                    sufficient to war-rant concern and additional studies.

                    1.3 Environmental Data Surveys

                    The circulation of the Gulf of Mexico is remarkable because of its variability
                    and intensity. The most prominent circulation features in the Gulf are (1) the
                    intense Loop Current System in the eastern Gulf and (2) an anticyclonic cell of
                    circulation in the western Gulf.Nearly two-thirds of the U.S. mainland and half
                    the area of Mexico drains into the Gulf of Mexico. The Mississippi and other
                    rivers with their associated nutrient and sediment loads have a great
                    influence on the Gulf. The prominent Gulf of Mexico circulation features and
                    the high fresh water input interact to make the Gulf of Mexico a very complex
                    environment. The goal of the GulfCet program is to develop an understanding
                    of environmental features and their effect on the spatial and temporal
                    distribution of cetacean species in the northwestern Gulf of Mexico.

                    Environmental data collection for the GulfCet Program consists of, eight
                    TAMUG hydrographic surveys, summer and winter National Marine Fisheries
                    Service (NMFS) surveys, and a synoptic overview by remote sensing. Satellite
                    images are from NOAA's Advanced Very High Resolution Radiometer (AVHRR)
                    polar orbiting satellites.

                                                                                                           7

                       1.3.1 Hydrographic Surveys (TAMUG1

                       The GulfCet program conducts four cruises each year, one cruise per season,
                       for two of the three years of the program. Each cruise has three purposes: a
                       visual survey of marine mammals, an acoustic survey using a towed
                       hydrophone array, and a hydrographic survey. A transect consisting of 14
                       North-South track lines is followed during the cruises. The hydrographic
                       survey was designed to sample the mesoscale-to- large scale features in the
                       GuIf.CTD stations are located at the 100 and 2000 m isobaths (except at the
                       Mexican border), and at 40 nautical mile intervals on each track line. The
                       location and spacing of the 84 XBT hydrographic stations was based on the 200,
                       350, 500, 800, 1000, and 1500 m isobath locations for each of the 14 North-South
                       track lines.

                       Data collected on each GulfCet cruise were obtained by lowering a CTD with a
                       rosette, XBT deployments, and LUMCON's continuously recording Multiple
                       Interface Data Acquisition System (MIDAS). For the first six cruises, a total of
                       503 XBT and 222 CTD stations were completed for a total of 723 stations. Vertical
                       profiles of salinity, temperature, oxygen, and beam attenuation coefficient
                       (transmissometry) were measured at every CTD station. In addition, 1753
                       chlorophyll and 583 salinity samples were obtained.

                       The temperature-salinity (T-S) plots show a remarkable uniformity below
                       17'C, indicating that the waters in the study area constitute essentially a single
                       system. Data from all the hydrographic stations reveal a distinct maximum
                       salinity greater than 36.60 psu and a minimum salinity less than 34.9 psu; this
                       excludes the surface fresh water near the Mississippi plume (which was as low
                       as 12.76 psu). These salinity signatures are characteristic of Subtropical
                       Underwater and Antarctic Intermediate Water, respectively. During the
                       GulfCet cruises, we have detected several ediies (Triton, "V", 11WIP and "X") with a
                       salinity greater than 36.60 psu, which is the hallmark of the Loop Current
                       eddies.

                       The observed depth of the 8'C and 15'C isotherms indicates the presence of
                       features such as the eddies. Regions where the temperature surface is deep
                       corresponds to anticyclonic (clockwise) circulation, and those regions where
                       the temperature surface is shallow corresponds to cyclonic (counterclockwise)
                       circulation. A prominent anticyclonic eddy is almost always present in the
                       western Gulf of Mexico. Small cyclonic eddies (cold water) are often associated
                       with the periphery of this dominant feature, and the 8'C isotherm topography
                       is the preferred detection tool for these eddies.

                       During the 1993 flood, the Mississippi plume was streaming to the east, which
                       is a rare occurrence. This event was visible on satellite images and was
                       confirmed by our hydrographic data (GulfCet, Cruise 6).
                       Our sampling grid has proven to be useful in sampling the meso-to-large scale
                       features of the Gulf of Mexico. We were able to detect all the major eddies
                       (Triton, "V", "W" and "X") and events present in the northwestern Gulf from
                       1992 to 1993. These anticyclonic eddies shed vorticity as regions of cyclonic
                       circulation when they feel bottom, and the companion cold-core (upwelling)
                       features probably are areas of greater production and may be preferred areas
                       for marine mammals. Further analyses on the hydrographic features and
                       environmental habitat of marine mammals continues.

                                                                                                       8

                     1.3.2 Remote Sensiniz and Geographic Information System

                     Stennis Space Center (NMFS) is providing remote sensing and geographic
                     information system (GIS) support for the GulfCet project. The GIS will be used
                     to integrate and analyze the various data types to explore possible
                     relationships between the distribution and abundance of marine mammals and
                     satellite and shipboard measurements of environmental variables in the Gulf
                     of Mexico.

                     Data are collected by the Advanced Very High Resolution Radiometer (AVHRR)
                     carried onboard the NOAA polar orbiting satellites and provide partial or full
                     coverage of the study area twice per day (one daytime and one nighttime
                     overflight) depending on the orbital path and cloud coverage. The data are
                     currently being obtained from the NOAA-1 1 satellite and are expected to be
                     available from NOAA-12 in the near future. With both satellites operating, up
                     to four images per day will be available.

                     The Naval Research Laboratory at Stennis Space Center maintains a satellite
                     receiving station and archive facility for AVHRR images and is the primary
                     source of data for the project. The satellite data are being processed into sea
                     surface temperature (SST) images. Each SST image is also being processed into
                     an absolute magnitude of the SST gradient image using 3 x 3 template masks
                     configured as Sobel operators and an arithmetic overlay operation. The visible
                     channels of the AVHRR from daytime overflights are also being processed into
                     turbidity images, primarily to examine the areal extent and location of edges of
                     the Mississippi River plume. A total of 199 AVHRR images have been acquired
                     (as of October 6th)for the study. The satellite data products, shipboard and
                     aircraft observations of marine mammals, and environmental data collected
                     aboard the vessels will be included as map layers in the GIS data base.

                     The GIS hardware consists of a Silicon Graphics UNIX workstation and
                     peripherals; software is the Advanced Geographic Information System (AGIS),
                     developed by Delta Data system, and the Science and Technology Laboratory
                     Applications Software (ELAS), developed by the National Aeronautics and
                     Space Administration. All of the digital map layers used in the GIS data base
                     will be registered to a portion of the Gulf of Mexico master image (GMMI) that
                     includes the GulfCet study area and thus encompasses the area from 26*to 31* N
                     Latitude and 8l'to 98* W Longitude. Some of the map layers tentatively
                     identified for use in the GIS data base can be stored as raster or vector data
                     files.

                     The GIS will be used for qualitative analysis of data structure by using such
                     functions as retrieval and classification and logical operations to create
                     interactive map displays, tabular summaries, and data plots in an effort to
                     visualize relationships between the distribution and abundance of cetaceans
                     and satellite and shipboard measurements of environmental variables. The
                     dimensionality of the data, i.e., the potential number of input variables for
                     multivariate statistical analysis, is expected to be large since GIS analysis tools
                     such as proximity measures will enable analysts to explore the data in ways
                     that would be virtually impossible using a conventional analysis methods.

                                                                                                     9

                     The initial exploratory analysis will be followed by a more formal, quantitative
                     analysis of the data using multivariate statistical techniques. Variables to be
                     used in the analysis will be exported from the GIS to one or more statistical
                     software packages: (1) the Statistical Analysis System (SAS) offering a wide
                     range of univariate and multivariate statistical procedures; (2) the Cornell
                     Ecology Programs provide cluster, detrended correspondence analysis, and
                     ordination techniques for ecological research; and (3) SpaceStat spatial
                     analysis software.

                                                                                                  10

                                                 11. INTRODUCTION

                    2.1 Background and Objectives

                    The Mineral Management Service (MMS) has the responsibility to assure that
                    oil and gas operations on the Outer Continental Shelf (OCS) Leases in the Gulf
                    of Mexico are conducted in a manner that reduces risks to the marine
                    environment. To meet their responsibilities under the Marine Mammal
                    Protection Act (MMPA) of 1972 and the Endangered Species Act (ESA) of 1973,
                    the MMS must understand the effects of oil and gas operations on marine
                    mammals. As the oil and gas industry moves into deeper water along the
                    continental slope in their continuing search for extractable reserves,
                    information is needed on the at-sea distribution, movements, behavior, and
                    preferred habitats of cetaceans, especially large and deep water species in the
                    Gulf of Mexico (Table 2.1). This study will help the MMS to assess the potential
                    effects of deepwater exploration and production on marine mammals in the
                    Gulf of Mexico.

                    The purpose of this study is to determine the seasonal and geographic
                    distribution and movements of cetaceans in areas potentially affected by
                    future oil and gas activities along the continental slope in the north-central
                    and western Gulf of Mexico. The study is restricted to the area bounded by the
                    Florida-Alabama border, the Texas-Mexico border, and the 100 m and 2,000 m
                    isobaths (Figure 2.1). In addition to conducting aerial and shipboard visual
                    surveys, the GulfCet Program has collected hydrographic data in situ and
                    remote sensing data to characterize the preferred habitats of cetaceans; in the
                    study area. When the analysis is complete, we will identify environmental
                    variables which correlate with the seasonal distribution of cetaceans. Finally,
                    we have attempted to tag and track a limited number of sperm whales using
                    satellite telemetry.

                    The GulfCet Program is a 3.25 year project which commenced on October 1,
                    1991 and will finish on December 31, 1994. Because the final surveys will not
                    be completed until April 1994, this report does not include models of cetacean
                    abundance or extensive correlations of cetacean distribution with
                    environmental variables. Instead, this interim report summarizes project
                    accomplishments and results for the first four aerial and six shipboard
                    surveys, two of the regularly scheduled Ichthyoplankton/Marine Mammal
                    survey cruises conducted by the National Marine Fisheries Service (NMFS),
                    and three sperm whale tagging cruises.

                    2.2 Program Participants

                    The GulfCet Program is administered by the Texas Institute of Oceanography
                    (TIO), which has scientific expertise in marine mammal biology, bioacoustics,
                    and oceanography through its Marine Mammal Research Program, the
                    Department of Marine Biology, the Department of Engineering Technology,
                    and the Department of Oceanography at Texas A&M University. Additional
                    expertise is provided by the NMFS at the Southeast Fisheries Science Center
                    which has extensive experience in aerial and shipboard surveys of marine
                    mammals in the Gulf of Mexico. This part of the project is contracted under a
                    separate Interagency Agreement between the MMS and NMFS. Finally, the

    11
    Balenidae
    Right Whale				Eubalaena glacials'
    Balaenopteridae
    Blue Whale				Balaenoptera musculus'
    Fin Whale				B. physalus'
    Sei Whale				B. borealis'
    Bryde's Whale			B. edeni
    Minke Whale				B. acutorostrata
    Humpback Whale			Megaptera novaeangliae'
    Physeteridae
    Sperm Whale				Physeter macrocephalus'
    Pygmy Sperm Whale			Kogia breviceps
    Dwarf Sperm whale			K. simus
    Xiphiidae
    Cuviers's beaked whale		Ziphius cavirosris
    Blainville's beaked whale	Mesoplodon densirostris
    Sowerby's beaked whale		M. bidens
    Gervais' beaked whale		M. europaeus
    Delphinidae
    Melon-headed whale		Peponocephala electra
    Pygmy killer whale		Feresa attenuata
    False killer whale		Pseudorca crassidens
    Killer whale			Orcinus orca
    Short-finned pilot whale	Globicephala macrorhynchus
    Rough-toothed dolphin		Steno bredanensis
    Fraser's dolphin			lagenodelphis hosei
    Common dolphin			Delphinus delphis
    Bottlenose dolphin 		Tursiops truncatus
    Risso's dolphin			Grampus griseus
    Atlantic spotted dolphin	Stenella frontalis
    Pantropical spotted dolphin	S. attenuata
    Striped dolphin			S. coeruleoalba
    Spinner dolphin			S. longirostris
    Clymene dolphin			S. clymene
    Table 2.1 Cetaceans of the Gulf Mexico.

                           ql
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                                                           MSTUDY AREA
                        0                              950                       900                        850
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                                                                                                       13

                      project includes scientists from the Hatfield Marine Science Center (HMSC) at
                      Oregon State University who have developed techniques to tag and track
                      whales using satellite telemetry. A list of the program's participants is shown
                      in Table 2.2.

                      The GulfCet Program has a Scientific Review Board (SRB) composed of five
                      experts who review and comment on the project's goals, methodologies, results,
                      analyses and conclusions. The current SRB members include:

                             J. Thomas, Ph.D.
                             Office of Aquatic Studies
                             Western Illinois University
                             Macomb, IL 61455.

                             H. Whitehead, Ph.D.
                             Department of Biology
                             Dalhousie University
                             Halifax, Nova Scotia, Canada B3H 4J1.

                             S. Reilly, Ph.D.
                             NMFS - Southwest Fisheries Center
                             8604 La Jolla Shores Dr.
                             La Jolla, CA 92038.

                             J. Cochrane, Ph.D.
                             Dept. of Oceanography
                             Texas A&M University
                             College Station, TX 77843.

                             K. Norris, Ph.D.
                             1985 Smith Grade
                             Santa Cruz, CA 95060.

                      Dr. N. Bray of the Scripps Institution of Oceanography, La Jolla, California, was
                      a previous SRB member who was replaced by Dr. J. Cochrane in September
                      1993.

                      2.3 Report Organization

                      The main text of this report is divided into two sections: Cetacean Surveys and
                      Environmental Data Surveys. Under the section on Cetacean Surveys, Mullin
                      and Hansen begin with a description of the aerial survey methods, results and
                      a discussion of the data acquired so far (Section 3.2). Jefferson and Wursig
                      continue with a discussion of the Texas A&M University shipboard visual
                      surveys of marine mammals (Section 3.3.1). Hansen and Mullin describe the
                      NMFS shipboard marine mammal surveys in Section 3.3.2., and Benson, Evans
                      and Norris present data acquired during the shipboard acoustic surveys using
                      a towed hydrophone array (Section 3.3.3). Finally, Mate describes the
                      techniques and difficulties of attaching satellite telemeters to sperm whales
                      (Section 3.4).

                                                                                             14

                  In the section on Environmental Data Surveys, Fargion begins with a
                  description of the hydrographic survey techniques, data analysis and a
                  discussion of the results from the first six shipboard surveys (Section 4.2). May
                  and Leming continue with a discussion of remote sensing data acquisition and
                  the Geographic Information System (GIS) that will be used in the final data
                  analysis for this project (Section 4.3).

                                     Randall W. Davis                 Program Manager                          TIO, TAMUG
                                     Bernd Wursig                     Deputy Prgm. Manager                     TIO, TAMUG

                                     Gerald P. Scott                  Program Manager                          NMFS, SFSC
                                     Giulietta Fargion                Data Manager                             TIO, TAMUG
                                     Robert Benson                    Principal     Investigator               TAMU, DET
                                     William Evans                    Principal     Investigator               TIO,TAMUG
                                     Larry Hansen                     Principal     Investigator               NMFS, SFSC
                                     Thomas Lemming                   Principal     Investigator               NMFS, SFSC
                                     Bruce Mate                       Principal     Investigator               HMSC, OSU
                                     Nelson May                       Principal     Investigator               NMFS, SFSC
                                     Keith Mullin                     Principal     Investigator               NMFS,SFSC

                                     Abbreviations:
                                     TIO, TAMUG           Texas Institute of Oceanography, Texas A&M
                                                              University at Galveston
                                     TAMU, DET           Texas A&M University, Department of Engineeri
                                                              Technology
                                     NMFS, SFSC          National Marine Fisheries service, Southeast
                                                                Fisheries Science Center

                                     HMSC, OSU            Hatfield Marine Science Center, Oregon State
                                                                University
    Table 2.2 Management structure, principal investigators and their affiliations.  			15

                                                                                                   16

                                              III. CETACEAN SURVEYS

                    3.1 Introduction

                    A major part of the GulfCet Program's field research consists of seasonal, line
                    transect surveys to determine the distribution and to estimate the abundance
                    of cetaceans in the study area. Three types of surveys are being conducted: 1)
                    visual surveys from an aircraft, 2) visual surveys from a ship, and 3) acoustic
                    surveys using a linear hydrophone array towed behind the visual survey ship.
                    Each of the three survey methods has its advantages and disadvantages in
                    terms of sighting marine mammals at sea. For example, visual surveys from
                    ships are very limited by available daylight and good weather (Beaufort 4 or
                    better), whereas the towed hydrophone array can operate day and night-in all
                    but the most severe weather conditions. However, the hydrophone array does
                    not always enable us to identify a particular species by its vocalizations and
                    cannot be used to determine pod size.   The visual surveys from an aircraft can
                    cover larger areas in a short period    of time, but also are limited to good
                    weather conditions. In addition, the limited fuel capacity of the aircraft
                    prevents it from reaching the 2000 m isobath (located 210 miles from shore)
                    along portions of the Texas coast. As   a result, the aircraft cannot survey the
                    entire study area. Each method of estimating abundance has inherent
                    limitations and assumptions. By using   three different survey methods, we will
                    arrive at the best estimates of seasonal distribution and abundance.

                    3.2 Aerial Surveys

                    3.2.1 Method

                    Four seasonal, aerial surveys were completed for the summer (10 August - 19
                    September 1992), fall (3 November - 16 December 1992), winter (1 February -
                    22 March 1993), and spring (25 April - 1 June 1993) seasons. Eight seasonal
                    surveys are scheduled. The surveys were conducted on the continental slope
                    in the U.S. Gulf of Mexico in an area bounded by Florida-Alabama state border,
                    the U.S. - Mexico border, the 100 in isobath and the 2,000 in isobath (east of
                    90*W) or the 1,000 m isobath (west of 90'W). The objective of the surveys was
                    to collect seasonal line transect and distributional data on cetaceans.

                    The survey platform of choice was a DeHavilland (DHC-6) Twin Otter, turbine
                    engine aircraft modified for marine mammal surveys. This aircraft was used
                    in MMS supported aerial surveys in the Gulf of Mexico during 1989 and 1990
                    (Mullin et al. 1990). A Twin Otter was not available for the first (summer)
                    aerial survey. Therefore, a Partenavia twin-turbine aircraft was contracted
                    from Aspen Helicopters (Oxnard, California). This aircraft was modified with
                    bubble windows, had transect line visibility, and was suitable for collecting
                    line transect data. However, the aircraft had a flight time of only 4.5 hours.
                    Because the transit time to the study area is long (about 1 hour), this limited
                    the amount of survey time per flight. A Twin Otter was available from the
                    NOAA Aircraft Operations Center for the fall, winter and spring surveys and
                    will be used for all subsequent GufCet surveys. The Twin Otter is also modified
                    with large bubble windows and has transect line visibility. The Twin Otter has
                    a flight time of 6.5 hours.

                                                                                                      17

                      Based on several considerations, including projected availability of acceptable
                      survey conditions and available funding, the study was designed to survey
                      about 6,500 transect km per season. Each season the study area was covered
                      uniformly. Transects from a random start were placed equidistance apart
                      across the study area. Transects were oriented perpendicular to the
                      bathymetry. Therefore, transects were placed north-south off Alabama,
                      Mississippi and Louisiana and east-west off Texas. Bases of operation were
                      Harlingen, Texas; Galveston, Texas; Lafayette, Louisiana; and Pascagoula,
                      Mississippi. A window of 45-days was allocated to each season, and surveys
                      were only conducted on days when flying conditions were safe and there were
                      none to few whitecaps.

                      Surveys were conducted using standard cetacean aerial survey methods. A
                      typical survey flight began at around 0800 in the morning and lasted about 6.5
                      hours. Three observers participated in each flight and rotated through two
                      observer positions and the computer station. Transect lines were surveyed
                      from 750 feet at a speed of 110 knots. When cetaceans were sighted, the
                      distance to the group from the transect line was measured with an
                      inclinometer. A dye marker was usually dropped to mark the position and the
                      aircraft was diverted to circle the group. The species was identified to the
                      lowest taxonomic level possible. The number of adults and calves were counted
                      and the location recorded. In compliance with our survey permit, the behavior
                      of the group at the time of the sighting and after the sighting were noted.
                      Data on survey conditions were collected (i.e., weather, water color, glare,
                      water clarity and sea state). Data were also collected on sea turtles and other
                      marine life sighted.

                      The survey team included Wayne Hoggard, Carolyn Rogers, Jon Peterson, Gina
                      Childress, Kevin Rademacher, Lesley Higgins, Carol Roden, Sean O'Sullivan and
                      Keith Mullin, all from the Southeast Fisheries Science Center. Steve Viada, of
                      the Minerals Management Service, participated in survey flights on 9
                      September 1992 and 15 March 1993. Behavioral observations of cetacean
                      groups from the aircraft were made on 12 February 1993 by Bemd Wdrsig,
                      Kathleen Dudzinski, and Dagmar Fertl from Texas A&M at Galveston.

                      3.2.2 Results and Discussion

                      During the summer season, all of the proposed 77 transect lines, totaling 6,571
                      km, were surveyed (Table 3.1). Weather caused major interruptions in the
                      survey on two occasions. The survey team disbanded in Galveston on 24 August
                      and the aircraft was moved inland while Hurricane Andrew was in the Gulf
                      Mexico. Because of the destruction in coastal Louisiana, the survey was
                      resumed from Pascagoula, and the Louisiana portion of the study area was
                      surveyed last. Because the survey was well ahead of schedule, both in terms of
                      flight hours and window-days used, the aircraft and survey team returned to
                      Pascagoula.    This was done in order to resurvey several transect lines
                      previously surveyed under marginal weather conditions and to provide the
                      locations of sperm whales for the GulfCet sperm whale tagging effort
                      scheduled to begin in early October. Fifty-seven cetacean groups were sighted
                      during this survey (Table 3.1). Six sightings were off-effort. At least 13 species
                      of cetaceans were sighted during the entire survey. Pantropical spotted
                      dolphins, bottlenose dolphins and dwarf/pygmy sperm whales were the most
                      commonly sighted species. Two mixed species groups were sighted:

                    0

                                                           Sum. 92    Fall 92    Win. 93    Spr. 93

                  no               Days in window             40        44         50         38
                  CD               Survey days                15        10         12         16
                                   Weather days               17        31         28         17
                                   Travel days                  6        3           4          1
                                   other days                   2        0           4          4
                                   Flight hours               97        80         90         100

                                   Transects completed        77        66         74         74
                                   Transects proposed         77        74         74         74
                                   Transect kilometers     6571        5506      6246       6370

                                   Number of sightings        51        24         37         51
                                   Number of animals         946       226         912      1159
                                   Off-effort sightings         7        2           4          6
                                   Number of species          13         9         10         12
                                   Group sightings rate       .78      .44         .59        .80
                                   (groups/100 km)
                                   Animal sighting rate    14.4        4.1       14.6       18.2
                                   (animals/100 km)
                                   Average group size      18.1        9.4       24.6       22.7

                   QQ

                                                                                                                00

                                                                                                                                                                                     19

                                                                                                                                            CO

                                                                                                                                            LO
                                                                  o M                                                                       C\j  C3

                                                                  CO                                                                             CO

                                                                                                                 4   44+

                                                                                                                                         + +

                                                                                                                                                 CO
                                                                  CD                                                                             C3
                                                                                                                                            C3   M
                                                                  CO                                                                        C)
                                                                  M   0                                                                          M
                                                                                                                                            LO
                                                                      M                                                                     C\j

                                   Figure 3.1. Location of each marine mammal group sighted (+)during
                                                         Summer 1992 GulfCet Aerial Survey.

                                                                                                   20

                    bottlenose dolphins and Risso's dolphins, and bottlenose dolphins and Atlantic
                    spotted dolphins. Cetacean groups did not appear to be uniformly distributed
                    in the study area (Figure 3.1). In addition to cetaceans, 27 sea turtles were
                    sighted including 23 leatherback sea turtles, an endangered species.

                    In the fall season, of the proposed 74 transect lines, only 66 were completed
                    because of poor weather (Table 3.1). A total of 3,395 transect km was surveyed
                    (88% of the proposed effort). High winds and rain were persistent throughout
                    the survey and caused major interruptions. Twenty-six cetacean groups were
                    sighted. Two sightings were off-effort. At least nine species of cetaceans were
                    sighted during this survey. Cetacean groups did not appear to be uniformly
                    distributed in the area surveyed (Figure 3.2). Four leatherback sea turtles and
                    one loggerhead sea turtle were sighted.

                    The winter survey window was extended from 45 to 50 days because of
                    mechanical problems with the aircraft on four days. The costs associated with
                    these days were absorbed by the NOAA Aircraft Operations Center. High winds
                    and rain were persistent throughout the survey window and caused major
                    interruptions in the survey. Twenty-eight days of the window had
                    unacceptable survey conditions. Surveys were conducted on 12 days and all of
                    the proposed 74 transect lines were completed (Table 3.1). A total of 6,246
                    transect krn was surveyed. Forty-one cetacean groups were sighted including
                    four off-effort sightings. At least ten species of cetaceans were sighted
                    including the first sightings of Bryde's/sei whale, striped dolphins, clymene
                    dolphins and spinner dolphins during the GulfCet aerial surveys. Other species
                    sighted included pantropical spotted dolphins, bottlenose dolphins,
                    dwarf/pygmy sperm whales, Risso's dolphins, Atlantic spotted dolphin, pilot
                    whales. Cetacean groups were found throughout the area surveyed (Figure
                    3.3). Four leatherback sea turtles and four chelonid sea turtles were sighted.

                    The spring survey was completed in 38 days. Weather was generally good
                    throughout the survey window, and there were no major interruptions. All of
                    the proposed 74 transect lines were surveyed (Table 3.1). Fifty-one cetacean
                    groups were sighted on-effort during the line transect surveys (Figure 3.4).
                    Six sightings were made off-effort. At least 12 species of cetaceans were
                    sighted during the entire window including the first sighting of Fraser's
                    dolphin during the GulfCet aerial surveys. Seventeen Fraser's dolphins were
                    observed in a tight group along with 400 melon-headed/pygmy killer whales
                    that were in many sub-groups spread out over a large area. There was also a
                    group of rough-toothed dolphins among these whales. This group of 400
                    cetaceans is the largest we have observed in the Gulf of Mexico. In addition to
                    cetaceans, three leatherback sea turtles and one chelonid sea turtle were
                    sighted. Except for three turtles, all of the leatherback sea turtles sighted
                    during the four seasonal surveys were aggregated near the Mississippi River
                    delta (Figure 3.5).

                    A total of 164 cetacean groups was sighted on-effort during the four surveys.
                    Twenty-five sightings were off-effort including a group of ten killer whales.
                    At least 18 species of cetaceans have been sighted to date. Bottlenose dolphins,
                    pantropical spotted dolphins,dwarf/pygmy sperm whales, also Risso's dolphins
                    were the most commonly sighted species. On-effort group sighting rates were
                    highest in summer and spring, and lowest in fall (Table 3.2). The summer,
                    winter and spring average group sizes of all cetacean groups sighted were
                    over twice the fall average. This resulted in a large difference in the sighting

                                                                                                                                                                                                  21

                                                                                                                                                                0
                                                                                                                                                           CNI  0

                                                                                                                   +         4+

                                                                                                                          -4f +

                                                                                                                                     +4

                                                                                                                                 4

                                                                                                                                                +         +.

                                                                                                                                                                C)
                                                                           C=)

                                                                           M
                                                                           CY)                                                                             C)   CT)
                                                                                                                                                           LD
                                                                               M                                                                           C\j

                                       Figure 3.2. Location of each marine mammal group sighted (+) during Fall 1992
                                       GulfCet Aerial Survey.

                                                                                              22

                                       0                                    0
                                       0                                    0
                                      0                                     LD 0
                                      C:)                                   CIJ0

                                      CO

                                                    :+
                                                       +  +

                                                              + +

                                                                +

                                                              4

                                                                   +  4

                                                                    ..P

                                      C3
                                                                               C3
                                      C)

                                      CO
                                      a) 0                                  C) CY)

                                                                            C\j

                    Figure 3.3. Location of each marine mammal group sighted          during
                               Winter 1993 GulfCet Aerial Survey.

                                                                                                                                                                                                     23

                                                                                 C)                                                                                   CM
                                                                                 0                                                                                    C\I

                                                                                 Cn                                                                                   C\j

                                                                                                            4                                                              CO

                                                                                                                                   +  +0

                                                                                                                              :+     +
                                                                                                                               +

                                                                                                                                +      +

                                                                                                                                    46-

                                                                            CO
                                                                            CO

                                                                                 Cl
                                                                            CO                                                                                        C\j CC)
                                                                            M 0                                                                                           a)

                                       Figure 3.4. Location of each marine mammal group sighted (+) during
                                                               Spring 1993 GulfCet Aerial Survey.

                                                                                           24

                                                                         0
                                       0                                 0

                                    O@                                   CD 0
                                    OM                                   C\J0

                                    M                                       CO

                                                       +
                                                      ++   +
                                                      + +#++   4
                                                      + +
                                                      + +

                                                                  +

                                    0                                       0
                                    01                                      0
                                       0                                 0  Go
                                    CT) 0                                0  CT)

                                       M                                 Di

                   Figure 3.5. Location       of leatherback sea turtles sightings during
                              Summer and Fall 1992, Winter and Spring 1993 GulfCet Aerial
                              Surveys.

                             M

                                                                                        Group                Depth                           n2
                      W r.L C/)                             Species               ni     size    range        (m)      range            S   F   W   S
                         (D
                             r)
                             CD
                      rjQ    CA                        Brdyels/sei    whale       1      1.0      -           213         -             0    0   1   0
                             0                                 sperm  whale      10      2.1     1-    4      934      499-1934         3    2   0   7
                         0 0                   dwarf/pygmy     sperm  whale      18      1.3     1-    3      743      151-1316         7    1   4   7
                             (D                           Mesoplodon sp.          1      4.0      -           630         -             1    0   0   0
                             a                               beaked whale         5      2.6     1-    4     1041      894-1316         1    2   0   2
                         @3,(D      melon-headed/pygmy       killer   whale       3    195.7    12-400        663      513- 835         1    0   0   2
                         (D                          false   killer   whale       1     35.0      -           974         -             1    0   0   0
                      M  (A
                                                             killer   whale       0     10.0      -           874         -             1    0   0   0
                                                               pilot  whale       6     15.1     5-  35       904      241-1876         3    2   0   2
                      > El   __
                      (D :9  OQ                   rough-toothed    dolphin        5     20.0     3-  48       829      85-1316          2    1   0   2
                         . -r                         bottlenose   dolphin       32     14.0     1-  60       337      65-1316          a    4 12  12
                                                         Risso's   dolphin       16     12.5     4-  33       704      234-2088         2    2   5   8
                                             Atlantic    spotted   dolphin       10     18.1     6-  42       252      126- 546         2    1   4   3
                         %.0 (D          pantropical     spotted   dolphin       19     40.0     5-100       1024      435-1815        13    1   3   6
                         !@j P                           striped   dolphin        1    150.0      -          1035         -             0    0   1   0
                      C4 OZ  :3                          spinner   dolphin        1    200.0      -          1055         -             0    0   1   0
                         F
                             QQ                          clymene   dolphin        3     29.0     9-  40       885      601-1298         0    0   1   2
                         - I
                         0-0                            Fraser's   dolphin        1     17.0      -           835         -             0    0   0   1

                                          bottlenose/Atlantic      spotted        3     12.3     2-  25       259      64-    329       1    0   1   3
                             N@*    striped/spinner/clymene        dolphin        5     19.6     2-  60       504      98-    795       2    1   2   0
                             (D                    unidentified    dolphin       12      4.5     1-  20       546      95-1613         11    4   4   2
                                             unidentified small whale             9      1.8     1-    3     1084      693-1748         6    1   0   2
                                             unidentified large whale             2      1.0     1-    1     1556                       2    0   0   0
                                              unidentified odontocete             4      1.0     1-    1      544      93-1356          0    4   0   0

                             (D
                                    I - total number of groups sighted            on-effort.
                                    2 - includes groups sighted off-effort.

                             M

                                                                                                    26

                    rate of animals in summer, winter and spring compared to fall. Much of the
                    decline in sightings in fall can be attributed to a decline in sightings of
                    dwarf/pygmy sperm whale and pantropical spotted dolphins. Of species
                    sighted more than once, pantropical spotted dolphins had the largest average
                    group size of all the species sighted, whereas dwarf/pygmy sperm whales had
                    the smallest. Because of their large average group size, the decline in
                    pantropical sightings accounted for much of the difference in the total
                    number of animals sighted in the fall compared to the summer. Only three
                    groups of pantropicals were sighted in winter. However, a group of 150
                    striped dolphins and a group of 200 spinner dolphins were seen in winter.
                    These two groups accounted for 38% of the cetaceans sighted in winter.
                    During the spring, groups of 175 and 400 melon-headed whales were sighted.
                    These groups accounted for 50% of the animals sighted in spring.

                    With sightings from all four seasons combined, cetacean groups were sighted
                    throughout the length of study area and at all water depths (Figures 3.1 to 3.4).
                    However, distinct species were found at different water depths (Table 3.2).
                    Bottlenose dolphins and Atlantic spotted dolphins were sighted primarily near
                    the shelf edge (200-300 m). Pantropical spotted dolphins and dwarf/pygmy
                    sperm whales were found in much deeper water (greater than 300 m). Pilot
                    whales and Risso's dolphins inhabited the greatest range of water depths
                    (greater than 1500 m).

                    The results of the four surveys are similar in several respects to those found
                    by Mullin et al. (1991) in the north-central Gulf during 1989 and 1990. The
                    only species identified in the earlier surveys that were not identified during
                    these surveys were the fin whale and Cuvier's beaked whale. Also, in both
                    studies, species were found at similar water depths. However, compared to
                    Mullin et al. (1991), there has been a paucity of sperm whale and Risso's
                    dolphin sightings during the GuIfCet surveys. In future surveys, based on data
                    from strandings and opportunistic sightings, it is reasonable to expect that
                    humpback whales or minke whales could be sighted.

                    3.3 Shipboard Visual Surveys

                    3.3.1 Visual Surveys: TAMUG

                    3.3. 1.1 Method

                    Two survey vessels, the R/V Longhorn and R/V Pelican, were used for the
                    Texas A&M University shipboard marine mammal visual surveys. On the first
                    cruise, we used the Longhorn, a 32-m, 210-ton research vessel operated by the
                    University of Texas. For the next five cruises, we used the Pelican which is
                    also 32 m long and has a displacement weight of 244 tons. The Pelican is owned
                    by the Louisiana Universities Marine Consortium (LUMCON).

                    The research vessel traversed the study area from either east to west or west to
                    east on each cruise at a speed of six knots when on transect and nine knots
                    when running between transect lines. The survey was conducted from the top
                    of the pilothouse on both vessels (observer eye height was approximately 7.7
                    m on the Longhorn and 8.9 m on the Pelican).

                                                                                                    27

                     Survey procedures followed closely those developed for dolphin surveys in the
                     eastern tropical Pacific. There were two, 3-person survey teams, one of which
                     was on duty during all daylight hours while in the study area. The teams
                     rotated every 2 hours. Two primary observers searched for marine mammals
                     through pedestal-mounted 25X150 Fujinon binoculars,while the third observer
                     acted as data recorder and assisted in searching with 7X binoculars. Each
                     primary observer searched a 1000 swathe, from 900 on their side to 100 past
                     the bow on the opposite side; the data recorder focused his/her effort near the
                     ship and around the trackline. Thus the total primary search path was 1800,
                     with a 200 overlap centered at the bow. Observers rotated positions every 30
                     minutes to avoid fatigue.

                     Sighting angle was recorded with the aid of a graduated scale at the base of the
                     binoculars, and radial distance to the sightings was either estimated by eye
                     (generally for sightings within a few hundred meters of the ship) or
                     calculated using reticles etched into the right eyepiece of the binoculars.
                     Radial distance was estimated from reticle readings by the equation:
                            R = x tan (arctan (89.173/4R) - 0.001088 r),

                     where R = radial distance (km), r = reticle reading, and x = eye height (in
                     nautical miles). Perpendicular distance was calculated from radial distance
                     and sighting by:

                            y = R sin o,

                     where y = perpendicular distance and o = sighting angle.

                     Sighting effort was conducted during daylight hours in which sighting
                     conditions were acceptable. Acceptable conditions were defined as Beaufort sea
                     states of less than 4 with good visibility. Sometimes rain, fog, glare, or
                     excessive ship roll interrupted the survey in sea states less than Beaufort 4.
                     During daylight hours when survey effort was suspended due to poor weather,
                     at least one observer was stationed on the bridge to record "off effort"
                     sightings which could be used for determining species distribution and
                     estimating herd size. Sighting and effort data were collected on standardized
                     forms developed by the NMFS.

                     In the final report, density will be calculated using line transect methods with
                     the computer program DISTANCE (Laake et al., 1993) Because sightings of
                     individuals for most species of cetaceans are not independent events, herds
                     will be considered the basic targets of the survey. We will use the 'rule of
                     thumb' suggested by Burham et al. (1980) and Buckland et al. (1993) for the
                     absolute minimum sample size for abundance estimation. This rule stipulates
                     that estimates should be based on no fewer than 30 sightings or detections.
                     Thus, any species with less than 30 "on effort" sightings will be pooled with
                     others to obtain adequate sample sizes. The basic line transect density formula
                     (Burnham et al., 1980) is:

                                                         D   n f(O
                                                               21,

                                                                                                     28

                    where D = density estimate of objects (herds), n = number or objects sighted,
                    f(O) = probability density function of the perpendicular distance.data, and L
                    total length of transect.

                    Multiplying the density estimate by the species or species group mean herd
                    size yields an estimate of individual density. Multiplying this value by the
                    total study area gives an estimate of the numerical abundance for individuals
                    of that species or species group:

                                                     N = n f(O) E(s) A
                                                          2 L g(O)

                    where N = abundance estimate, E(s) = mean herd size, A = total study area and
                    g(O) - the probability that an object on the trackline is detected (Buckland et
                    al., 1993). In most cases, g(O) is assumed to be 1; however this is probably not
                    true for long-diving species, and thus g(O) must be calculated and factored into
                    the equation for these species.

                    The effective strip width (ESW), an index of the sightability of the species (or
                    groups), will also be computed for each species group with a density estimate
                    as:

                                                         ESW
                                                                f(o).

                    Because extremely large coefficients of variation could result from the survey
                    effort being stratified by season to produce separate line transect estimates,
                    seasonal differences will be examined instead by computing sighting rates for
                    different seasons (Le, number of herds or individuals per 1000 km of trackline
                    surveyed), and comparing these between seasons.

                    3.3.1.2 Fesults and Discussion

                    A total of 340.81 hours of sighting effort was conducted on the first six cruises
                    (Table 3.3). This represents 4587.49 kilometers of transect line surveyed. In
                    addition, 17.08 hours of independent observer (10) effort were conducted. The
                    independent observer effort will be used to test the assumption that g(O) = 1
                    (i.e. that all animals on the trackline are detected). For long diving species,
                    such as sperm whales and beaked whales, such an assumption is probably
                    invalid, and a correction for submerged animals will be included in the final
                    abundance estimates for these species (see Barlow, 1993).

                    A total of 258 marine mammal sightings were made within the study area on
                    the first six cruises (Table 3.4). Of these, 182 were "on effort" and are usable in
                    the density and abundance estimates. The 76 "off-effort" sightings can be used
                    only in estimating mean herd size, and will not be used to estimate density and
                    abundance.

                    Based only on the sightings from these six cruises, the only species with an
                    adequate sample size for abundance estimates is the bottlenose dolphin (32 on
                    effort sightings). It is likely that the number of sperm whale sightings will
                    equal to at least 30 by the end of the project. All other species will have to be

                             CD
                             @Ij
                             !IJ
                             CA

                          0$
                          'I
                          0
                          CL
                          CD
                          100                 Cruise              1             2             3            4             5             6             Total

                          CL
                          m                   Hours
                          0
                          C't                   of             39.65         79.28        37.13         41.32        68.13         75.30              340.81
                          0                   Effort

                          (D 0
                             5                Hours
                             (D               of 10                                                                    6.66        10.42               17.08
                                              Effort
                             P
                             -h               Km
                                              of            487.40         1036.56 535.86 529.39 956.62 1041.66 4587.49
                                              Effort

                             0
                             0
                             CL

                             CL

                             0

                              species                     On Effort         Off Effort        Total

                              Sperm Whale                     25                11              36
                              Cuvier's beaked whale            2                 0               2
                   0
                              Pygmy sperm whale                1                 0               1
                              Dwarf sperm whale                1                 0               1
                              Short-finned pilot whale         0                 1               1
                              False killer whale               2                 1               3
                              Melon-headed whale               2                 0               2
                              Risso's dolphin                  5                 0               5
                              Fraser's dolphin                 2                 0               2
                              Rough-toothed dolphin            1                 1               2
                              Bottlenose dolphin              32                13              45
                   OQ
                              Atlantic spotted dolphin         5                 2               7
                              Pantropical spotted dolphin     17                 9              26
                   OQ         Spinner dolphin                  1                 0               1
                              Clymene dolphin                  5                 1               6
                              Striped dolphin                  3                 0               3
                              Unid. cetacean                  11                 3              14
                              Unid. large whale                2                 0               2
                              Unid. Kogia                      2                 1               3
                              Unid. beaked whale               5                 3               8
                              Unid. Kesoplodon                 3                 3               6
                              Unid. small whale               22                 3              25
                              Unid. dolphin                   33                24              57
                              Total                           182               76             2SO

                                                                                                                 C)

                                                                                                     31

                       pooled based on the number of sightings, taxonomic relationships, and
                      general habitat types (Wade and Gerrodette, in press). For example, oceanic
                      species of Stenella (pantropical spotted, striped, spinner, and clymene
                      dolphins) all occur in large herds and may be pooled, but the fifth species
                      (Atlantic spotted dolphin) is a continental shelf species that is found in small
                      herds and would not be included in the above grouping.

                      There have been several unexpected results from these shipboard,visual
                      surveys. First, the most common species observed along the outer edge of the
                      continental shelf in this region of the Gulf of Mexico is the bottlenose dolphin,
                      not the Atlantic spotted dolphin as indicated by Schmidly (1981). Sperm whales
                      and pantropical spotted dolphins were, by far, the most common cetaceans
                      seen in oceanic waters. The only exception to this occurred on the sixth cruise
                      in which very few pantropical spotted dolphins were sighted. The prevalence
                      of sperm whales as the most abundant large cetacean was expected. However,
                      previous research had not indicated that the pantropical spotted dolphin was
                      the most common oceanic species. Mullin et al. (1991) found Risso's dolphin to
                      be more common in parts of the Gulf. However, their study was not directly
                      comparable to ours, since it occurred in shallower water (mostly along the
                      upper continental slope) and in a very limited geographic area.

                      Another unexpected finding is the paucity of short-finned pilot whales.
                      Strandings and past sighting records would have led us to believe that this is
                      one of the most common, medium-sized cetaceans offshore (Schmidly, 1981).

                      Several poorly-known species have turned out to be moderately common
                      (beaked whales, pygmy and dwarf sperm whales, melon-headed whale, and
                      Fraser's and clymene dolphins). Both melon-headed whales and Fraser's
                      dolphins were almost completely unknown in the Gulf of Mexico before this
                      study began, each represented by one or two standings. The first live sightings
                      of these species in the Gulf (and for Fraser's dolphin, the first for the entire
                      Atlantic Ocean) were recorded during this project (Leatherwood et al., in press;
                      Mullin et al., submitted). The clymene dolphin was well-known in the Gulf
                      from strandings previous to this project, but also was poorly-represented by
                      live sightings (Jefferson and Odell, in prep.)

                      3.3.3 Vi5ual Surveys: NMFS RV Oregon if

                      3.3.3.1 Method

                      The Southeast Fisheries Science Center (SEFSQ has conducted two of four
                      planned vessel surveys aboard the NOAA RIV Oregon II as part of the SEFSC
                      contribution effort to the GulfCet Program. The first survey was conducted
                      from April 21 to June 8, 1992 (spring-summer), and the second survey took
                      place from January 4 to February 14, 1993 (winter). Both surveys were
                      designed to collect: 1) marine mammal sighting data to estimate abundance,
                      distribution and diversity, and 2) environmental data to evaluate factors which
                      may affect the distribution, abundance and diversity of marine mammals.
                      These surveys are also part of the SEFSC's overall marine mammal research
                      program. Similar vessel surveys have been conducted annually during the
                      spring-summer in the northern Gulf of Mexico since 1990.

                                                                                                 32

                   The spring-summer survey was conducted in three separate legs, with the first
                   two legs covering the off-shelf waters of the northern Gulf between 8Y- 960W
                   longitude. The third leg concentrated on the GulfCet study area between 870-
                   960W longitude. The winter survey consisted of three legs, all essentially
                   within the GulfCet study area between 87'-96' W longitude. The major
                   difference in sampling between the two surveys was in the visual sampling
                   strategy. During legs I and 11 of the spring-summer survey, visual sampling
                   occurred during daylight hours along a cruise track that was sampled 24 hours
                   a day for ichthyoplankton; daylight transects could be latitudinal or
                   longitudinal, or a combination of both (Figure 3.6 and 3.7). Ichthyoplankton
                   sampling did not occur on leg III of the spring-summer survey or during
                   daylight hours on all legs of the winter survey. This resulted in visual
                   sampling on only longitudinal transects (Figures 3.6 to 3.11).

                   Visual sighting data were collected by two teams of three observers during
                   daylight hours, weather permitting (Le, no rain, Beaufort sea state less than
                   6). Each team had at least two members experienced in shipboard marine
                   mammal observation and identification techniques. Two observers searched
                   for marine mammals using high-power (25 X), large format "Bigeye"
                   binoculars mounted on the ship's flying bridge.           The third observer
                   maintained a search of the area near the trackline with handheld binoculars
                   and recorded data. Sighting data were recorded with a computer in the format
                   required for line-transect analysis. Information collected included species,
                   herd-size, perpendicular sighting distance, and data on environmental
                   conditions (Le, Beaufort sea state, sun position, etc.) which could affect the
                   observers' ability to sight animals. Ancillary data included behavior and
                   associated animals.

                   In general, environmental stations were located every 30 minutes of latitude
                   or longitude along the cruise track. The stations included CTD/STD, hydrocasts
                   to a maximum depth of 500 m. An XBT was dropped halfway between the
                   environmental stations. A thermo-salinograph operated throughout the entire
                   cruise; surface water salinity and temperature were recorded every minute of
                   time. Data from the hydrographic survey are in the SEAMAP (NOAA) data base.

                   3.3.2.2 Results and Discussion

                   A total of 6,154 transect kilometers were visually sampled for marine mammals
                   during the spring-summer survey despite weather and mechanical problems
                   which caused the loss of about 15 effort-days. The visual sampling resulted in
                   273 sightings of at least 20 species of cetaceans (Table 3.5). The bottlenose
                   dolphin and the pantropical spotted dolphin were the most frequently sighted
                   species and accounted for 21% and 19%, respectively, of identified sightings.
                   Risso's dolphins , sperm whales , and dwarf sperm whales were the next most
                   frequently sighted, and accounted for 11%, 8%, and 8%, respectively, of
                   identified sightings.

                   The winter survey resulted in the visual sampling of 4,017 transect kilometers,
                   although weather conditions significantly hampered the sampling effort. The
                   survey was suspended on two days due to severe weather (sea state greater
                   than Beaufort 6), and reduced on eleven additional survey days when average
                   daily sea state was greater than Beaufort 4. At least 10 cetacean species were
                   observed in a total of 46 sightings (Table 3.5). Sperm whales were the

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                               sightings during Leg 3 of spring-summer survey, NOAA ship.

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                                                                   sightings during Leg 2 of winter surveysummer survey, NOAA
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                              SPECIES                          SUMNER-SPRING              WINTER

                              Balaenoptera edeni                      1
                              Balaenoptera edenilborealis             3
                              Physeter macrocephalus                 19                      9
                              Kogia breviceps
                                                                      5                      1
                              Kogia simus
                                                                     18                      -
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                 P.- "                                               12
                 ca           Mesoplodon sp.
                   e)                                                 6
                              Mesoplodon densirostris                 1
                              Unidentified Ziphiid                    2
                              Peponocephala electra                   2
                              Feresa attenuata                        2
                              FeresalPeponocephala
                   UQ                                                 1
                              Pseudorca crassidens
                                                                      1
                              orcinus orca
                                                                      1
                              Globicephala macrorhynchus              3                      2
                              Steno bredanensis                       5
                              Lagenodelphis hosei                     1
                   0          Turslops truncatus                     48                      5
                              Grampus griseus
                                                                     24                      -
                              Stenella frontalls                      7                      6
                   (D         TursiopsIStenella frontalis             1
                   ca
                              Stenella attenuata                     43                      6
                              stenella coeruleoalba                   7                      2
                              Stenella longirostris                   6
                   W          Stenella clymene                        6                      2
                   r.         Stenella sp.
                                                                      1                      1
                              Unidentified dolphin                   27
                              Unidentified small whales               4
                              Unidentified odontocete                16                      2

                              TOTALS                                273                      46

                                                                                                    40

                    most commonly sighted cetaceans, with 9 sightings (25% of identified
                    sightings). Atlantic spotted dolphins and pantropical spotted dolphins were
                    the next most common with six herd sightings each (17% each of identified
                    sightings).

                    The sighting distribution data from the spring-summer survey were combined
                    with that from the spring-summer surveys from 1990-92 for a preliminary
                    evaluation of distribution patterns. This evaluation does not correct for effort.
                    Sighting data from the winter survey were not included because of possible
                    seasonal differences. Figure 3.12 illustrates the sightings of all cetaceans
                    during the spring-summer surveys. In general, it appears that sightings were
                    more common in the central portion of the northern Gulf. Sightings also
                    appear to be more common in the eastern side of the survey area than in the
                    western side. However, more survey effort has been expended in the central
                    and eastern portions of the area, and the apparent differences in sighting
                    distribution may reflect effort.

                    The Stenella sp., with the exception of the Atlantic spotted dolphin, were
                    sighted most frequently in the deeper, off-shelf waters of the survey area.
                    Figure 3.13 illustrates the sightings of the pantropical spotted dolphins; other
                    Stenella (with the previously noted exception) display the same pattern. The
                    sighting distribution of the Atlantic spotted dolphin was quite different with
                    all sightings located on the edge of the continental shelf (Figure 3.14).

                    Sightings of bottlenose dolphins, Risso's dolphins,and Atlantic spotted dolphins
                    all appeared to occur quite frequently along the edge of the continental shelf.
                    However, whereas Atlantic spotted dolphins were sighted only along the shelf
                    edge, bottlenose dolphins were also seen frequently on the continental shelf
                    while Risso's dolphins were also seen in the deeper Gulf waters (Figures 3.14 to
                    3.16).

                    Members of the sperm whale family were sighted both along the shelf edge
                    and in the deeper waters of the survey area. Kogia sp. sightings were located
                    throughout the deeper waters, with no apparent pattern. Sightings of sperm
                    whales, however, showed an apparent disjunct distribution with sightings in
                    Mississippi and DeSoto canyons and a band along the southern edge of the
                    survey area (Figure 3.17). This apparent distribution should be interpreted
                    with caution, since what appears to be a band along the southern edge may
                    only represent the tip of a distribution that was not fully observed. The
                    distribution could quite possibly extend beyond the limits of the survey area.

                    Other species, such as pilot whales, rough-toothed dolphins, false killer
                    whales, beaked whales, Bryde's whale, and others were seen too infrequently
                    to justify evaluation of sighting distributions on a species basis. Overall,
                    however, nearly all of these species appear to occur most frequently in the
                    deeper waters and not on the continental shelf or shelf edge. The exception to
                    this pattern was Bryde's whale, with nearly all sightings occurring in or
                    along the edge of DeSoto canyon.

                    Four species not seen on the previous SEFSC marine mammal vessel surveys
                    were observed on the present surveys. Blainville's beaked whale, the melon-
                    headed whale and Fraser's dolphin were all sighted on the spring-summer
                    survey, and melon-headed whales were seen on the winter survey. These
                    observations represented some the first documented sightings of these species

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                    Figure 3.13. Locations      of S. attenuata groups sighted during SEFC
                                marine mammal cruises in the northern Gulf of Me.-dco: 1990-
                                1992.

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                     Figure 3.15. Locations (+) of Tursiops truncatus groups sighted during SEFC
                                 marine mammal cruises in the northern Gulf of Me.,dco: 1990-
                                 1992.

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                              during SEFC marine mammal cruises in the northern Gulf of
                              Mwdco: 1990- 1992.

                                                                                                    47

                     in the Gulf of Mexico (Fraser's dolphins were observed earlier in 1992 during a
                     Texas A&M shipboard visual and acoustic survey). Melon-headed whales were
                     also observed during the winter survey, and the first SEFSC vessel sightings of
                     killer whales occurred during the spring-summer survey.

                     3.3.3 Acoustic Surveys: TAMUG

                     3.3.3.1 Method

                     A linear hydrophone array was towed behind the Texas A&M University visual
                     survey ship (i.e. the Longhorn or the Pelican) to record the distinctive
                     underwater vocalizations of cetaceans. This passive acoustic survey technique
                     enabled us to identify cetaceans in the vicinity of the ship in order to
                     determine their distribution and to estimate their abundance. This
                     hydrophone array has been used in previous studies to determine the
                     distribution of cetaceans in the Eastern Tropical Pacific (Thomas et al., 1986).

                     The hydrophone array is made of three sections; a deck cable, a tow cable, and
                     a "wet section" which contains the active elements (hydrophones) of the array
                     (Figure 3.18). The 30 m deck cable connects the shipboard electronics to the
                     active array via the tow cable at the winch. The 184 m tow cable (1.04 inch
                     outer diameter) has 32 pairs of electical wires and is negatively buoyant. The
                     235 m "wet section" of the array is composed of four sections: a forward ".dead
                     section", fore and aft vibration isolating mechanisms (VIMs), fore and aft high
                     frequency sections with depth and temperature sensors, and a middle-low
                     frequency section. The VIMs are elastic sections designed to reduce low
                     frequency, self-induced noise.

                     The towed array has 195 hydrophones organized into 18 groups. These groups
                     are tuned to six different frequency bands. In the low frequency section
                     (Figure 3.19), eight groups of hydrophones are tuned to 30 Hz, one group at 480
                     Hz, and a third group at 3.84 kHz. In each fore and aft high frequency section,
                     there are hydrophone groups tuned to 5, 10, and 15 kHz. The hydrophones of
                     each tuned section are separated along the array by a distance equal to the
                     wavelength of the tuned frequency in order to increase sensitivity (as
                     indicated by its directivity index). For example, the 20 AQ 10 hydrophones of
                     the 5 kHz tuned segment are each separated by 33 cm to maximize the
                     directivity index at that frequency.

                     The towed array has an overall frequency sensitivity from 10 Hz to 30 kHz,
                     with maximum sensitivities at 30 Hz, 480 Hz, 3.84 kHz, 5 kHz, 10 kHz, and 15 kHz.
                     Because of the speed (3.75 inches per second) used to record the signals, the
                     actual bandwidth varies from 10 Hz to 12.5 kHz. The array has maximum
                     sensitivity in a ringed pattern perpendicular to the long axis of the array and
                     very little sensitivity either fore or aft. It therefore detects little ship-
                     generated noise, particularly the higher frequencies (Figure 3.20).

                     The towed array is connected to a model RA-44A Portable Geophysical
                     Amplifier (SIE, Inc.) (Figure 3.21). The amplifier has 18 channels, each with
                     its own gain control, and, for the high frequency channels, variable cut-off
                     filters. The amplified signals are recorded on an eight channel Racal Store V
                     analog tape recorder. The recorder has seven tape speeds ranging from 0.47 to
                     30 inches per second (ips) and three bandwidth settings for each channel. We

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                                                                                                   52

                     recorded at 3.75 ips, which resulted in a 2.5 kHz bandwidth for the low
                    frequency channels and a 12.5 kHz bandwidth for the high frequency
                    channels. At this tape recorder speed, we recorded approximately 200, 40-
                    minute tapes on each cruise.

                    Eight channels of the tape recorder were used in recording the output from
                    the array. The operator kept a logbook of the frequency range for each
                    recorded channel, the amplifier gain, and the tape recorder attenuation.
                    These tape recorder settings were noted at the beginning of each 40-minute
                    tape along with the date, time, track number, tape speed, and ship's speed.
                    Once this information was written on a data form, the operator monitored the
                    array's acoustic signal both visually with the real-time spectrograph and
                    acoustically with either headphones or speakers. Whenever a signal was
                    received, the tape speed, time, and geographic location were recorded in a
                    logbook.

                    While at sea, electronic signals were processed on an AST 386 microcomputer
                    using SIGNALTm software which had a subroutine (RTS) that provided real time
                    spectrograms on a color monitor. Signal analysis at the Center for Bioacoustics
                    (Texas A&M Universtiy) was performed using a Kay Elemetrics model 5500 dual
                    channel, real-time spectrograph. This instrument can simultaneously produce
                    spectrograms (frequency vs time displays with relative amplitude signified by
                    shades of gray), oscillograms (time vs amplitude), and spectra (frequency vs
                    amplitude). Frequency and time domain analyses can be analyzed further for
                    species identification.

                    The towed array was deployed whenever the ship was on a transect line. It was
                    towed at a uniform speed of 5 knots for the first four cruises and 6.5 knots for
                    cruises five and six. The speed of the vessel determines the depth of the array,
                    with an approximate depth of 18 m at a speed of 5 knots and 12 m at 6.5 knots.
                    The array was brought onboard whenever the vessel stopped (i.e. for CTD
                    casts).

                    The first step in our analysis of acoustic contacts was to verify that the
                    recorded signal was from a marine mammal and, when possible, to identify the
                    species. At this time, we can identify certain species based on our library of
                    known vocalizations. We assume that when an animal is seen, vocalizations
                    heard concurrently are produced by it. However, if more than one species is
                    seen simultaneously, then the source of the signal is listed as unknown. All
                    tapes are reviewed in the laboratory by one of the acoustic technicians, who
                    checks the written record made at sea for the location of the acoustic contact
                    on the tape. The technician then enters the revolution number, time,
                    geographic location, presumed species identity (including unknown), and any
                    comments into a computer database.

                    Three steps will be used to identify unknown vocalizations. First, a series of
                    acoustic parameters will be defined that characterize aspects of the
                    vocalizations of known species. These parameters will include direct
                    measurements of the signal (such as duration) and derived values (such as
                    mean bandwidth assymetry). Algorithms have been written that automatically
                    implement these parameters on the computer. Secondly, signals from
                    identified animals will be analyzed using these algorithms to train
                    multivariate statistical programs using jack-knife procedures. The level of
                    accuracy will depend on the size of the training set. For some species (i.e.

                                                                                                     53

                     Fraser's dolphin), there are very few recordings. In fact, for this species we
                     made the first recordings. In other cases (i.e., pantropical spotted dolphin), we
                     have a large collection of recorded vocalizations. Identification algorithms for
                     all species for which we have recorded vocalizations will be completed by
                     February 1994.

                     3.3.3.2 Results and Discussion

                     The acoustic contacts for the first four cruises are summarized in Table 3.6. A
                     complete list which includes the species, date and location of each acoustic
                     contact is included in Volume 2 (Appendix). It is important to note that the
                     locations shown for marine mammals are for "first contact", which may not be
                     the final, computed location for these contacts. This is a problem primarily for
                     sperm whales, which can be heard over 20 miles from the vessel.

                     Cruise 1: All 14 transect lines were surveyed, with only line 3 left unfinished
                     due to poor weather. We recorded 2S7 tapes and made 49 acoustic contacts with
                     biological sources. Of th-ese, seven were identified as sperm whales, six as
                     dolphins, three as Stenella sp., and 22 were unidentified dolphins. Acoustic
                     contacts occurred throughout the study area, although there were fewer at the
                     southern ends of transect lines 1-4 (Figure 3.22). Recordings were made in the
                     presence of bottlenose dolphins, pantropical spotted dolphins, clymene
                     dolphins, and sperm whales. Measurements were also made of sound pressure
                     levels on each channel of the Racal tape recorder using a B & K meter. Ocean
                     depth and the presence of the deep scattering layer were recorded from the
                     ship's depth gauge when animals were encountered. Seven species (bottlenose
                     dolphins, pantropical spotted dolphins, clymene dolphins, Altantic spotted
                     dolphins, Risso's dolphins, sperm whales, and Cuvier's beaked whales) were
                     visually identified.

                     Cruise 2 Over the course of 13 transect lines, we recorded 226 tapes and made
                     70 contacts with biological sources (Figure 3.23). We made recordings from
                     five species, all of which had been recorded on the previous cruise.
                     Recordings were made from four sperm whales including one visual sighting
                     of six animals. Eight of the 70 acoustic contacts were sperm whales, two were
                     bottlenose dolphins, three were Stenefla sp., and 48 were unidentified dolphins
                     or other cetaceans. Among the recordings of unidentified cetaceans, some
                     may have been pulses from an unidentified Mesoplodon and from whistles
                     killer whales. As with the first cruise, there were few acoustic contacts at the
                     southern ends of transect lines 1-5; most of these were sperm whales. Likewise
                     the central northern region of the study area also contained few contacts,
                     with the highest number of encounters in the eastern half of the study area.
                     Sperm whales were heard in the same location on transect lines 2 and 12
                     (ocean depth 700-1200 m) as occurred on Cruise 1 four months earlier.

                     Cruise 3: Continuous recordings were made on 13 transect lines resulting in 47
                     acoustic contacts (Figure 3.24). This represented more acoustic contacts per
                     unit distance than on previous cruises. Because the visual survey effort was
                     greatly reduced due to bad weather, we had only two contacts (sperm whales
                     and pantropical spotted dolphins) when the animals were both seen and their
                     vocalizations recorded. Because of the unique character of sperm whale pulses,
                     we were able to identify them immediately. Ten sperm whale contacts were
                     made on this cruise compared to seven on Cruise 1 and eight on Cruise 2. The

              (IQ

                    98  97  96  95  94  93 92  91  90  89  88

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                                                                                                      57

                      sperm whale pulses were often heard for over an hour. Sperm whales have
                      been encountered in the same area (27"11 N latitude, 95*30 W longitude) on
                      transect line 2 on the first two cruises. At the south end of line 2, we also
                      recorded and observed what appeared to be a large, solitary sperm whale,
                      perhaps a bull. Sperm whales also have been observed repeatedly along
                      transect line 12 near the mouth of the Mississippi River. However, on this
                      cruise we did not hear sperm whales on transect lines 11 or 12, but we did hear
                      them on line 14 as well as the area in between transect lines 12 and 13 in deep
                      water.

                      Cruise 4: Recordings were made on along all 13 transect lines resulting in 76
                      acoustic contacts. Simultaneous observations and recordings were made for
                      sperm whales (2) and pantropical spotted dolphins (5). Overall, we had 8
                      acoustic contacts with sperm whales, including contacts along transect line 12
                      where we've heard whales on previous cruises. The acoustic contact with
                      sperm whales on line 2, where we saw many animals, was 35 miles to the south
                      of contacts on previous cruises. We also had two acoustic contacts with
                      presumed pilot whales. One of these contacts was concurrent with a sperm
                      whale contact. As with previous cruises, we had many contacts with
                      unidentified dolphins, typically whistles at night. The unidentified dolphins
                      may be pantropical spotted dolphins, but confirmation must await further
                      analysis.

                      3.3.3.3 Summ

                      A total of 4,496 miles (96% of the planned distance) was acoustically surveyed
                      during Cruises 1-4. The 4V6 which was not surveyed resulted from equipment
                      failure or poor weather. We had a total of 246 acoustic contacts on 910 recorded
                      tapes (see Table 3.6). This is equivalent to 0.0547 acoustic contacts/survey mile.
                      Many of these contacts represent more than one animal.

                      The most common marine mammal acoustic contacts (149) have been
                      unidentified dolphins.These contacts were generally whistles recorded
                      primarily at night or during poor weather conditions when visual
                      identification was impossible. Of the 64 identified marine mammal acoustic
                      contacts, 3 3 (5 1 %) have been from sperm whales.

                      A preliminary analysis of the distribution of sperm whale acoustic contacts for
                      Cruises 2, 3 and 4 was conducted by a graduate student (T. Sparks). He defined a
                      contact as any sperm whale signal received after more than 30 minutes of
                      silence. He identified a total of 25 contacts during 472.3 hours of acoustic
                      sampling or 0.053 sperm whale contacts/hour of effort. There were no visual
                      sperm whale contacts during 157.7 hours of concurrent visual effort, although
                      there were five, off-effort visual contacts. These five visual contacts occurred,
                      on average, 64.4 minutes (range 7-206 minutes) after the acoustic contact. The
                      frequency of acoustic contacts did not correlate with time of day or transect
                      line number.

                      The locations of identified marine mammal acoustic contacts show some
                      preliminary patterns. Sperm whales (Figure 3.25) have been encountered on
                      transect line 2 on all four cruises. We have also heard sperm whales in the
                      same area on line 12. Overall, the majority of the sperm whale contacts have
                      been off the mouth of the Mississippi River or on the western side of the study

                                             CIQ

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                                     Cruise                                  species                                                        Total
                                                                                                                         Other      Unid.
                                                    P.            T.         Stenella        Dolphins       Unid.      Biological
                                              macrocephalus   truncatus                                    Cetacean
                                                                         attenuata   sp.   other  Unid.

                                        1           7             6          2        1             22         3           3          5       49
                                        2           8             2          4        3             47         1           2          3       70

                                        3           10            2          1                      22         8           2          1       47

                                        4           8                        5                      58         3           2                  76

                                      Total         33            10         16       4      1      149        15          9          9

                                                                                                      61

                       area. There have been no contacts on transect lines 7 and 9 and only one on
                       lines 5 and 10.

                       Contacts with bottlenose dolphins have occurred along the shallower,
                       northern edge of the study area, whereas contacts with pantropical spotted
                       dolphins have been in the deeper water along the eastern continental slope
                       (Figure 3.26). There has been only one pantropical spotted dolphin contact
                       west of transect line 10, that being at the extreme southern end of transect
                       line 5.

                       These distribution patterns are reflected in the average water depths for
                       acoustic contacts. Pantropical spotted dolphins and sperm whales were found
                       in the deepest water (mean depths = 1667 m and 1272 m, respectively) while
                       bottlenose dolphins occurred in more shallow waters (mean depth = 3 15 m).
                       Several of the deeper bottlenose dolphin contacts occurred off the mouth of
                       the Mississippi River, where the continental shelf is narrow (i.e. 10 miles).

                       3.4 Satellite Tagging of Sperm Whales

                       3.4.1 Introduction

                       Oregon State University was responsible for placing Satellite-linked Time-
                       Depth Recorders (SLTDRs) and location only by satellite telemeters on sperm
                       whales to determine their movements, diving behavior and preferred habitat.
                       To accomplish this goal, three cruises were undertaken:two in the Gulf of
                       Mexico (October 1992 and June 1993) and one in the Galapagos (March 1993).
                       The Galapagos cruise was intended as a test for tag deployment and attachment.

                       3.4.1 Method

                       The satellite telemeters used for this project were designed and built by Oregon
                       State University using Wildlife Computers TM controller boards and TelonicsTM
                       ST-6 Platform Transmitter Terminals (PTTs) and housed in a stainless steel
                       cylinder (5 cm diameter, 19 cm long, 0.8 kg in weight). The exterior of the
                       housing had attachments which consisted of two stainless steel rods (12.7 cm
                       long, 0.6 cm diameter) with one pair of folding toggles mounted behind
                       double-edged blades at the end of each rod.

                       The transmitters were attached to whales with compound crossbow capable of
                       generating 150 lbs. of force. The satellite telemeter was attached to a "C"-
                       shaped cup at one end of an aluminum shaft. The shaft with the satellite
                       telemeter was then fired from the crossbow. A line (20 lbs. test) attached to the
                       aluminum shaft enabled the satellite telemeter to be recovered if it missed the
                       whale. Once the satellite telemeter was attached to the whale, the shaft was
                       designed to fall off.

                       The Telonics PTTs transmitted a 400 milliwatt (mW) signal every 40 seconds
                       when in the programed "on" mode. To conserve battery power, the tag was
                       equipped with a saltwater switch so that it transmitted only at the surface. A
                       small, VHF radio transmitter was attached to the housing to enable real-time
                       tracking at sea. The VHF transmitters were tuned to specific frequencies, had
                       different repetition rates, and transmitted continuously.

                                                                                                       62

                     All satellite telemeters were identifiable by a code transmitted to the satellite as
                     part of a 256 bit data stream. The SLTDRs collected data over eight, three-hour
                     summary periods daily. These data included three histograms: depth of dives,
                     duration of dives, and time spent at various depth ranges. Other data for each
                     three hour period included the longest dive, deepest dive, duration of deepest
                     dive, temperature at deepest depth, longest surface duration uninterrupted by
                     a submergence of greater than six seconds, and total surface duration.

                     Transmission was scheduled for four, two-hour periods (eight hours) daily. A
                     status message was relayed in lieu of the collected data after every 15
                     transmissions. This message provided information on battery voltage, sea
                     surface temperature, number of transmissions, current zero depth offset, and
                     a current assessment of saltwater resistance. All messages included a cyclic,
                     redundancy code checksum for error detection purposes.

                     The Wildlife Computers pressure transducer and software were tested
                     extensively using a relay box to simulate dives to different depths and
                     durations. The satellite telemeter housing was tested to 2000 m in a pressure
                     bomb. Based on these tests, we decided to pot the transmitter, batteries and
                     controller board in epoxy to provide greater structural strength.

                     3.4.3 Results

                     Cruise-L The first tagging cruise was conducted from 30          September to 14
                     October, 1992. We used was the RIV McGrail, an 82 foot long converted Coast
                     Guard Cutter operated by Texas A&M University. The McGrail arrived in
                     Venice, IA on September 31 and left for Galveston Sept 14, 1992. We were able
                     to work for only 4.5 of the 13 days due to poor weather and equipment failures
                     on the vessel.

                     Our cruise covered an area where previous GulfCet cruises and aerial surveys
                     had observed sperm whales, but had to remain within the ship's operational
                     limits (offshore to 100 miles from Venice). Visual contact with sperm whales
                     was made only once for about four hours. On October 9, 8 - 10 sperm whales
                     were sighted. We approached the whales and observed little reaction to the
                     boat. Unfortunately, we did not get close enough to tag any animals. The
                     animals showed very little reaction to our approaches, and there were no
                     instances of "alarm" responses. The whales changed their course only slightly
                     when the ship approached to within 8 m.

                     Cruise-L. This cruise was conducted in the eastern Pacific off the Galapagos
                     Islands from 20-31 March, 1993. We used the RIV Odyssey, a 92 foot long
                     sailboat owned and operated by the Whale Conservation Institute. Three
                     SLTDRs were supplied by the GulfCet Program. The other operating costs for
                     this cruise were provided by Oregon State University's Marine Mammal
                     Foundation.

                     The purpose of this cruise was to test techniques to approach and attach
                     SLTDRs to sperm whales. The waters around the Galapagos were an ideal test
                     ground because, unlike the Gulf of Mexico, the seasonality and distribution of
                     large numbers of sperm whales had been well documented for this area.

                                                                                                    63

                      We located and followed several hundred sperm whales over a five day period
                      using visual and acoustic contacts. We were able to make close approaches to
                      sperm whales without overt changes in their behavior. Whales occasionally
                      changed direction during very close vessel approaches but did not show a
                      "flight" response to the boat.

                      On March 26, we succeeded in attaching a SLTDR to a sperm whale.The
                      telemeter was placed about 0.5 m from the whale's dorsal ridge and appeared to
                      be flush against the animal's skin. The animal not appear to startle or take
                      flight after attaching the telemeter but continued its initial submergence
                      pattern and surfaced only a few minutes later 100 m from the boat.

                      Two other tagging attempts were unsuccessful: in the first instance, the
                      telemeter hit the dorsal ridge of the animal and glanced off. In the second
                      instance, the animal arched suddenly so the tag missed its target completely.
                      The animal then fluked and broke the retrieval line which would otherwise
                      have allowed us to recover the tag.

                      This was an excellent learning cruise in which we developed approach
                      techniques which were used later in the Gulf of Mexico. We learned that our
                      method of attachment works for sperm whales but that care needs to be taken
                      to avoid tagging in the area near the dorsal ridge.

                      Cruise 3a The second GulfCet tagging cruise. used the RIV Acadiana, a twin
                      diesel, 58 foot long vessel chartered from LUMCON (Louisiana Universities
                      Marine Consortium). The Oregon State University team arrived in Cocodrie, on
                      June 1, 1993. Construction of a tagging platform and some remaining LUMCON
                      charter activities were completed by June S. The ship left Cocodrie on June 6
                      and returned on June 29. We were able to work for 14 of the 24 days; 4 days
                      were used for transit between Cocodrie, and Port Eads, LA (June 6,14,16 and 29);
                      1 day the ship fulfilled a previous charter obligation (June 15); 5 days were
                      spent in port during tropical storm Arlene (June 17-21).

                      The tagging platform was constructed from a 2-piece, 9 m long, fiberglass
                      extension ladder with a pulpit at the end made of wood. The platform was
                      stabilized with tension wires and extended 3.5 m off the starboard side of the
                      ship. The platform was extremely stable, and it was possible to pull it in while
                      underway and during docking.

                      Visual observations, the towed hydrophone array and sonabuoys were used to
                      locate whales. The areas surveyed were based on previous GulfCet aerial and
                      shipboard sightings. During 24-hour operation, scientific watches were held
                      from 0600-2000 daily with two OSU persons on watch at all times. All cetacean
                      sightings were recorded. At night, the scientific crew stood 2-hour watches
                      which included acoustic stations (monitoring a suspended hydrophone) and
                      maintaining vessel safety.

                      When whales were spotted, one observer remained in visual contact with the
                      animals while the other scientists prepared the tagging equipment, 35 mm
                      cameras, video recording equipment and data sheets. VHF radio headsets were
                      worn by the captain and scientific crew to communicate on the whale's
                      location and to coordinate the ship's movements for tagging.

                                                                                                 64

                   The vessel covered 2331.4 km searching for sperm whales (Figure 3.27). Sperm
                   whales were seen on seven days and heard on 11 days. The number of whales
                   ranged from 4-22 per day with up to 8 animals seen at one time (Tables 3.7 and
                   3.8). A maximum of 87 individuals were seen during the cruise. Animals were
                   sighted most often in the afternoon.

                   Animals were approached to within 75 m at which time the vessel was slowed
                   and one engine shut down to reduce noise for the final approach. The sperm
                   whales we found were quite small. Most were less than 8 rn in length and were
                   considered too small to tag; a few were up to 8 m. Even these presented a small
                   target and needed to be within 5 m of the ship and perpendicular to the
                   tagging platform (approximately parallel to the vessel's starboard side) before
                   a shot could be attempted. Positioning was critical for successful tagging.
                   Because there are subdermal anchors at each end of the cylindrical tag, the
                   tag's trajectory must be perpendicular to the whale or the tag will not attach
                   properly. Tagging attempts were made only when the animal's back was well
                   out of the water and not arched.

                   Two animals were tagged. The first whale (about 8 m in length) was tagged on
                   7 June with an SLDR. Only one message was heard from this tag.            Photos
                   revealed that the tag was located on the dorsal ridge with the forward tyne of
                   the housing implanted 5-8 cm in the blubber and the rear tyne only 2.5 cm. We
                   believe that this tag fell off the animal shortly after attachment      due to
                   incomplete penetration of the tynes into the blubber. The second         animal
                   (about 7 rn in lenght) was tagged on 11 June with a location-only telemeter.
                   The telemeter placement was good. Although penetration was not complete, it
                   was judged to be adequate. We have conducted further shock tests but at
                   present do not know why this telemeter failed.

                   All other opportunities (12-13 and 23-24 June) for tagging were with animals
                   judged to be too small.We saw no whales on four of the last five days despite
                   excellent weather and sighting conditions (25-29 June).

                   A seismic vessel, the Acadian Commander, began seismic surveys on 23 June in
                   an area where whales had been routinely seen (Figures 3.28 and 3.29). The
                   seismic surveys were expected to continue for 30 days. Whales were seen on
                   the periphery of the seismic survey area on the 23 and 24 June, but not in the
                   middle of the area where we had seen many whales regularly before the
                   seismic work began. No whales were seen in or near this area after 24 June (9
                   survey days). While the change we observed in whale distribution may have
                   been due to normal movements or a change in prey concentration, it did
                   coincide with the onset of seismic activity. Therefore, there may be a cause-
                   and-effect relationship, and the possibility can only be resolved with further
                   investigation. Very few other cetaceans or sea birds were seen during this
                   cruise.

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                                                                                                                                                                 6-29 June 1993              R/V Acadian
                                                                                                                                                                       Oregon State University

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                                                                                                                                                                                 Nautical miles
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                                                                                                                                                                                24 June      12 June

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                                             6/7/93       1608                 29002. 35/88001. 54         7
                                             6/7/93       1710                 29002. 23/88003. 50         3
                                             6/7/93       1900                 29002.26/88005. 15          4
                                             6/12/93      1520                 28049. 32 /88035. 48        3
                                             6/12/93      1750                 28050.40/88035.7 1          3
                         CD
                                             6/12/93      1810                 28040. 68/88039. 67         1
                                             6/12/93      1945                 28050. 36/88040. 09         4
                                             6/13/93      0815                 28042. 47/88052. 71         2
                         CM                  6/13/93      0828                 28042. 01/88052 . 24        2
                                             6/13/93      0845                 28041. 68 /88052. 14        1
                         z                   6/13/93      1637                 28043 .85/88022. 01         3
                         CD                  6/13/93      1740                 28046.40/88026. 66          1
                         @4                  6/13/93      1900                 28050. 47/88034. 07         5
                                             6/13/93      1915                 28050. 29/88034. 40         4
                                             6/23/93      1240                 28056. 25/88011. 17         2
                                             6/23/93      1345                 28057. 70/88012. 43         2
                                             6/23/93      1426                 29000. 12/88012 .9 1        3
                                             6/23/93      1430                 29000. 39/ 88012 . 8 1      3
                                             6/23/93      1508                 29000. 13/ 88012 . 3 3      1
                                             6/23/93      1725                 28056. 56/88011. 26         3
                                             6/23/93      1740                 28056. 70/88011. 57         1
                                             6/23/93      1835                 28059. 58 /88016. 94        4
                                             6/23/93      1908                 28058. 59/88017. 53         3
                                             6/24/93      1145                 29000. 37 /88012 . 4 1      2
                                             6/24/93      1308                 29002 . 34/88012. 09        2
                                             6/24/93      1347                 29004. 42/88011. 47         3
                                             6/24/93      1450                 29003 . 63 /88011. 62       4
                                             6/29/93      1805                 2803 9. 70/8804 1. 00       2
                                             6/29/93      1830                 28038. 80/8804 1. 55        2

                                                                                                                                                 00

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                              Date         Time(CDT) Lat/Long                        What                    Number

                      10      6/7/93       1420        28040. 64/89005. 69           Tursiops truncatus      2
                      (D
                      0 '     6/7/93       1940        28036.70/88043 . 03           Stenella attenuata      15-20
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                              6/12/93      1350        28054.29/88023. 85            Stenella clymene        25-30
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                              6/23/93      1930        28059. 40/88017. 64           Lagenodelphis hosei     3
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                              6/24/93      0745        29007. 13/87058. 52           Stenella attenuata.     25
                      :3      6/24/93      1010        28058. 11/88002. 64           Stenella attenuata      35-40
                      (D
                              6/24/93      1345        29004.80/88010. 94            Steno bredanensis       8
                              6/27/93      1920        28046.40/88057.8.t            Grampus griseus         5

                                                                                                   70

                    3.4.4 Discussion

                    Previous information about sperm whales in the Gulf has indicated that they
                    are sparsely distributed and have very small pod sizes. The sperm whales
                    sighted during the tagging cruises were in a patchy distribution over a large
                    geographic region and were usually in loose groups of 2-8 animals. ,

                    Of particular interest was the small size of the sperm whales sighted. We do not
                    believe that any of the animals were over 8 m. Four whales appeared small
                    enough to be calves which may have been weaned recently. At one point, we
                    were in an area with about eight small animals at the surface. We stayed in
                    this area for two hours and saw no evidence of any larger animals. Large
                    animals would be expected if these small ones were part of a mixed group of
                    females, calves and juveniles. This juvenile group social structure may be
                    unique to this area. It has never been reported in the scientific literature and
                    certainly deserves more attention. We have examined the stranding records
                    and concluded that sperm whales of normal size do exist in the Gulf, and we
                    were not merely looking at a population of small individuals.

                    While searching for sperm whales in the Gulf of Mexico, we obtained some
                    circumstantial evidence that active seismic vessels may affect the distribution
                    of sperm whales. During five of our first nine survey days, we consistently
                    sighted sperm whales, generally in a localized geographic area. During this
                    time, the Acadian Commander was preparing to begin seismic testing. During
                    the first two days of seismic activity (34 guns shooting every 10 seconds at 1800
                    psi, 24 hours a day), we located only a few sperm whales on the margins of the
                    seismic survey area. We found no whales for the next five days in that region.
                    Although our observations represent circumstantial evidence, the change in
                    whale sightings after the onset of seismic activity is sufficient to warrant
                    concern and additional studies.

                    We attached satellite telemeters to two small animals on this cruise: an SLTDR
                    and a location-only telemeter. The lack of penetration of the tynes appeared to
                    be due to the tough skin and blubber on the animal's dorsal ridge. The small
                    size of the animals that we tagged may have exacerbated this problem. Our
                    attachment methods have worked very well on right whales and bowhead
                    whales but may have to be modified for sperm whales.

                    3.4.5 Recommendations

                    1. To determine when and where adult sperm whales occur, it would be helpful
                       if aerial and shipboard observers could obtain length estimates of all sperm
                       whales sighted.

                    2. The possible connection between active seismic vessels and sperm whale
                       movements deserves further study. If successful, satellite tracking would be
                       a valuable tool to examine animal movements in areas of seismic surveys.

                    3. If possible, satellite telemeter attachments should be tested on sperm whale
                       carcasses.

                    4. Alternative satellite telemeters and attachments need to be considered for
                       tagging small individuals.

                                                                                                       71

                      S. Because of the difficulty in finding sperm whales, future tagging cruises
                         should dedicate at least six weeks of sea time to tag animals. The vessel should
                         be certified to operate beyond 100 miles from shore.

                      6. Aerial surveys should be coordinated with tagging cruises to initially locate
                         sperm whales most efficiently.

                      7. Photo and video-documentation of the tagging process is important to verify
                         the quality of tag attachment, document potential tagging reactions, and
                         identify individuals which are tagged.

                      8. Aerial and shipboard surveys and tagging efforts should obtain information
                         on the schedules and operational areas of seismic surveys. If MMS does not
                         have a program to monitor seismic surveys, it should consider one so that
                         marine mammal surveys can use this important variable to interpret
                         results.

                                                                                                    72

                    3.6 References for Seclion III

                    Barlow, J. 1993. The abundance of cetaceans in California waters estimated
                      from ship surveys in summer/fall 1991. Southwest Fisheries Science Center
                      Administrative Report LJ-93-09, 39 pp.

                    Buckland, S.T., D.R. Anderson, K.P. Burnham, and J-L 1,aake. 1993. Distance
                      Sampling: Abundance Estimation of Biological Populations. Chapman and
                      Hall, 446 pp.

                    Burnham, YP., D.R. Anderson, and J.L Laake. 1980. Estimation of density
                      from line transect sampling of biological populations. Wildlife Monographs
                      72, 202 pp.

                    Jefferson, T.A. and K.D. Odell. In prep. Biology of the clymene dolphin
                      (Stenella clymene) in the Gulf of Mexico. journal of Mammalogy.

                    Laake, J.L, S.T. Buckland, D. R. Anderson, and K.P. Burnham. 1993. DISTANCE
                      User's Guide Version 2.0. Colorado Cooperative Fish & Wildlife Research Unit,
                      72 pp.

                    Leatherwood, S., T.A. Jefferson, J.C. Norris, W.E. Stevens, L.J. Hansen, and K.D.
                      Mullin. In press. Occurrence and sounds of Fraser's dolphins
                      (Lagenodelphis hosei) in the Gulf of Mexico. Texas journal of Science.

                    Mullin, K.D., T.A. Jefferson, LJ. Hansen, and W. Hoggard. Submitted. First
                      sightings of melon-headed whales (Peponocephala electra) in the Gulf of
                      Mexico. Marine Mammal Science.

                    Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, and C. Rogers. 1991. Cetaceans
                      on the upper continental slope in the north- central Gulf of Mexico. OCS
                      Study MMS 91-0027, 108 pp.

                    Schmidly, D.J. 1981. Marine mammals of the southeastern United States coast
                      and the Gulf of Mexico. Biological Services Program FWS/OBS-80/41, 165 pp.

                    Thomas, J.A. S.R. Fisher, L.M. Ferm et al. 1986. Acoustic detection of cetaceans
                      using a towed array of hydrophones. Rep Int. Whal. Commn. (Special issue 8)
                      139-148.

                    Wade, P.R. and T. Gerrodette. In press. Estimates of cetacean abundance in the
                      'eastern tropical Pacific. Reports of the International Whaling Commission
                      43.

                                                                                                     73

                                              IV. ENVIRONMENTAL DATA

                      4.1 Introduction

                      The circulation of the Gulf of Mexico is remarkable because of its variability
                      and intensity. The most prominent circulation features in the Gulf are the
                      intense Loop Current System in the eastern Gulf and an anticyclonic cell of
                      circulation in the western Gulf (Nowlin and McLellan, 1967; Behringer, et al.,
                      1977; Merrell and Vazquez, 1983). The Loop Current's path and extent of
                      intrusion into the Gulf varies with season, but reaches a maximum in the
                      summer, at which time an anticyclonic eddy separates from the loop and drifts
                      westward (Hofmann and Wortley 1986; Merrel and Vazquez 1983). High
                      fluctuations in frequency of eddies (from 8 to 17 months) have been reported
                      by Behringer et al. (1977). Different types of eddies have also been described,
                      including anticyclonic eddies and cyclonic-anticyclonic eddy pairs (Merrell
                      and Morrison, 1981; Brooks and Legeckis, 1982). Less is known about the
                      circulation in the western Gulf relative to the eastern Gulf (Merrell and
                      Morrison, 1981). Two main mechanisms of the observed anticyclonic gyre in
                      the western Gulf have been suggested. The first is that the gyre is maintained
                      by loop eddies which have drifted to the west (Ichiye, 1967; Schroeder, et al.,
                      1974), and the second is that the gyre is driven by a curl of wind stress (Nowlin
                      1972). An equal contribution of both mechanisms has been suggested by
                      Merrell and Morrison (1981).

                      Nearly two-thirds of the U.S. mainland and half the area of Mexico drains into
                      the Gulf of Mexico (Weber, et al., 1990). The Mississippi and other rivers with
                      their associated nutrient and sediment loads have a great influence on the
                      Gulf. The seasonality cycle of the Mississippi River is shown in Figure 4.1
                      (mean flow plus or minus one standard deviation). The mean river flow is
                      computed at Vicksburg, Ms. using daily data from 1932 to 1986. Figures 4.2 and
                      4.3 show the flow of the river from November 1978 to June 1986, with a time
                      series of chlorophyll pigments from the Coastal Zone Color Scanner (CZCS). It
                      is clear that the Mississippi River plays an important role in the interannual
                      variations of chlorophyll and in developing areas of high productivity in the
                      Gulf. The 1992-1993 Mississippi River flow was anomalous in its seasonality and
                      flow (United States Department of the Interior, United States Geological Survey,
                      1992 and 1993). Therefore, the Mississippi could affect the spatial and temporal
                      distribution of cetaceans in the Gulf of Mexico.

                      The prominent Gulf of Mexico circulation features (such as the Loop Current,
                      the 1992-1993 eddies Triton, "U", Velasquez (V), and Whopper (W), and the high
                      fresh water input of May and August -September, 1993) interact to make the
                      Gulf of Mexico a very complex environment. The goal of the GulfCet Program is
                      to develop an understanding of environmental features and their effect on the
                      spatial and temporal distribution of cetacean species in the northwestern Gulf
                      of Mexico. Environmental data collection for the GulfCet Program consists of,
                      eight (TAMUG) hydrographic surveys, summer and winter National Marine
                      Fisheries Service (NMFS) surveys, and a synoptic overview by remote sensing.
                      Satellite images are from NOAA's Advanced Very High Resolution Radiometer
                      (AVHRR) polar orbiting satellites. Stennis Space Center (NMFS) is providing
                      the remote sensing as well as the Geographical Information System (GIS)
                      support for the GulfCet Project.

                                             18000

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                                                                                                          77

                       4.2 Hydrographic Survey: TAMUG

                       4.2.1 Introduction

                       This section presents an overview of the extensive, multivariate hydrographic
                       data set collected during the GulfCet Program. Its objective is to provide a
                       foundation on which the reader can understand the methods of data
                       acquisition and steps taken to process the data. Pre-analysis corrections or
                       adjustments are identified and discussed.

                       Data collected during the program will be submitted to the National
                       Oceanographic Data Center (NODC) and will be available to the public from that
                       source. The integrated analyses of the data discussed below form the basis for
                       the process syntheses presented in section 4.2.6.

                       4.2.2 Transect and Cruise Design

                       The GulfCet Program conducts four TAMUG sponsored cruises each year, one
                       cruise per season, for two of the three years of the program. Each cruise has
                       three purposes: a visual survey of marine mammals, an acoustic survey using
                       a towed hydrophone array, and a hydrographic survey. A transect consisting
                       of 14 North-South track lines (Figure 4.4) is followed during the cruises. The
                       hydrographic survey was designed to sample the mesoscale to large scale
                       features in the Gulf. The choice of location and spacing of the 50 CTD
                       hydrographic stations for this study is based on the following:

                          a) estimates of spatial scales in the study region (eg., slope eddy radii of
                               50-100 km) from bibliographic references;
                          b) acoustic and visual survey constraints;
                          c) ship time constraints;
                          d) similar survey patterns in MMS other Programs: LATEX A,
                              LATEX B, and LATEX C;
                          e) CTD time estimates;
                          f) previous historical data.

                       As a result, CTD stations are located at the 100 and 2000 in isobaths (except at the
                       Mexican border), and at 40 nautical mile intervals on each track line. The
                       location and spacing of the 84 XBT hydrographic stations was based on the 200,
                       350, 500, 800, 1000, and 1500 in isobath locations for each of the 14 North-South
                       track lines.

                       4.2.3 Summaries of Cruises 1-6

                       The first TAMUG GulfCet cruise (Cruise 1), was a sixteen day spring cruise
                       (April 15-May 1, 1992), aboard the University of Texas at Austin's ship, RIV
                       Longhorn. This cruise was divided into three legs as the result of personnel
                       transfers and inclement weather delays. The following are the dates for each
                       leg of the cruise: leg 1: April 15 -17; leg 2: April 20 -21; and leg 3: April 23 -May
                       1, 1992. No underway navigation or meteorlogical system was available for this
                       cruise. Technical difficulties in the initial CTD casts resulted in fewer CTD
                       stations being sampled than had been planned. The nature of these problems
                       was found to be flooding in the main CTD housing, and partial failure of the

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                                                                                                      79

                      pumping system. A total of 15 CTD casts, 96 XBT stations, 115 salinity samples,
                      and 127 chlorophyll samples were completed. CTD casts were to a maximum
                      depth of 1000 m for this cruise and all cruises following. Further details have
                      been published in a report entitled "GulfCet Cruise 01 Hydrographic Data",
                      Technical Report 93-01-T (Fargion and Davis, 1993).

                      Following Cruise 1, all GulfCet cruises were conducted aboard the RIV Pelican
                      of the Louisiana University Marine Consortium (LUMCON). This vessel
                      presented several advantages, such as increased stability for the visual survey
                      of marine mammals, increased laboratory space, and a continuously recording
                      navigation and meteorlogical system.

                      GulfCet Cruise 2, a fourteen day summer cruise, took place between August 10-
                      24, 1992. Track (transect) line 1 was dropped from the station plan for this
                      cruise and in all succeeding cruises due to vessel schedule constraints. A total
                      of 44 CTD casts and 78 XBT stations were completed, and 85 salinity samples and
                      273 chlorophyll samples were taken. Further details are available in "GulfCet
                      Cruise 02 Hydrographic Data", Technical Report 93-02-T (Fargion and Davis,
                      1993).

                      GulfCet Cruise 3, a fifteen day fall cruise, took place November 8-22, 1992. Track
                      line 10 and a portion of line 11 were not sampled due to inclement weather. A
                      total of 39 CTD casts and 75 XBT stations were completed, resulting in 75 salinity
                      samples and 425 chlorophyll samples. Technical Report 93-03-T (Fargion and
                      Davis, 1993), "GulfCet Cruise 3 Hydrographic Data", gives complete details
                      regarding the data for this cruise.

                      The fourth GulfCet Cruise, a fifteen day winter cruise, occurred between
                      February 12-27, 1993. 80 salinity and 476 chlorophyll samples were collected
                      from 44 CTD casts. 84 XBT stations were completed as well. Details of this cruise
                      have been published in "GulfCet Cruise 4 Hydrographic Data", Technical
                      Report 93-04-T (Fargion and Davis, 1993).

                      GulfCet 5, a ten day spring cruise, took place May 24-june 5, 1993. Track 2 as
                      well as track 1 were dropped from the station plan for this cruise due to vessel
                      scheduling constraints. To maximize the workable time, CTD's were cast only to
                      a maximum of 500 m. 75 XBT stations and 42 CTD casts were completed,
                      providing 84 salinity and 111 chlorophyll samples.

                      The second summer cruise, the eleven day GulfCet cruise 6, occurred August
                      27-September 5, 1993. Tra6k lines 2 and 3, in addition to line 1, were dropped
                      from the station plan for this cruise as a result of ship schedule restrictions. A
                      depth of 800 m was the maximum depth to which the CTD was lowered to
                      maximize available time. A total of 38 CTD casts and 94 XBT stations were
                      completed, resulting in 144 salinity and 341 chlorophyll samples.

                      Figure 4.5 summarizes the total number of CTD and XBT stations completed for
                      each line for cruises 1-6. A total of 503 XBT and 222 CTD stations were completed
                      for a total of 723 stations. In total, 1753 chlorophyll and 583 salinity samples
                      were obtained. Data for cruises 1-4 are included in the accompanying Volume
                      II (Appendix) to this report as well.

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                                                                                                      81

                      4.2.4 Shipboard Measurements and Procedures

                      Data collected on each GulfCet cruise were obtained by lowering a CTD with a
                      rosette, XBT deployments, and LUMCON's continuously recording Multiple
                      Interface Data Acquisition System (MIDAS) (Walser, et al., 1992).

                      4.2.4.1 CTD/Rosette Cast$

                      Vertical profiles of salinity, temperature, oxygen, and beam attenuation
                      coefficient (transmissometry) were measured at every CTD station. Once on
                      station and after the vessel had come to a complete stop, the CTD/Rosette was
                      lowered to just below the surface. Bottom depth was checked, and time and
                      location were recorded. During the downcast, temperature, salinity and beam
                      attenuation coefficient were graphically dispayed in real-time as a function of
                      depth. CTD data were acquired at 24 Hz. Once near the bottom, the CTD/Rosette
                      was stopped and held for 5 minutes at that depth before starting the upcast.
                      During this time, the sampling depths for the upcast were selected. The upcast
                      was identical to the downcast except the instrument was stopped at the selected
                      sampling depths, and the Niskin bottles were tripped. The CTD/Rosette was
                      lowered to the sea floor, or to a maximum depth of 1000 m. At stations less than
                      500 m, in situ fluorescence was also measured. Secchi disk and environmental
                      data were gathered using World Meteorlogical Organization (WMO) codes.

                      The water sample depth selection was based on chlorophyll sample criteria and
                      followed these general guidelines:

                      -100 m stations: water samples were taken at depths of 0, 5, 15, 20, 30, 40, 50,
                        60,70, 80, 90, and 100 m.

                      -All other stations: sampling depths were 0, 10, 20, 30, 40, 55, 70, 85, 100, 125,
                         150, and 1000 m.

                      Occasionally, due to special circumstances (on cruise 06 nutrient samples were
                      collected) or to the presense of unusual hydrographic features, sample depths
                      were added or deleted. A salinity sample was always taken from the shallowest
                      and deepest bottle.

                      Water samples for chlorophyll analysis were filtered at sea using GF/F filters
                      (4.7 cm. diameter, and 0.7 micron retention size). The filters were stored in
                      liquid nitrogen and a -80'F freezer until analyzed at TAMUG. GulfCet
                      chlorophyll samples were analyzed for chlorophyll a and phaeopigments
                      using a Turner Designs Fluorometer and following a modified Strickland and
                      Parsons (1972) procedure. Precision of chlorophyll and phaeopigment
                      analysis was +/- 0.01 gg L:1. Replicates of chlorophyll samples for line 4 were
                      given to the MMS LATEX-A Program for HPLC pigment analysis.

                      4.2.4.2

                      .XBT's were launched at depths of 200, 350, 500, 800, 1000, and 1500 meters along
                      each track line. At an XBT station, either a Sparton of Canada or Sippican T-7,
                      T-10, or T-20 XBT probe (depending on the depth) was deployed while the ship
                      was underway. Ship speed during deployment did not exceed 7-8 knots. Extra
                      XBT deployments (one or two) per cruise coincided with CTD casts. Additional

                                                                                                  82

                    XBT's were launched during some marine mammal sightings, for acoustic
                    array calibration, and when unusual hydrographic features were detected
                    (i.e., GulfCet cruise 6).

                    4.2.4.3 Multiple Interface Data AcQuisition Systgm (MIDAS)

                    A continuous recording of navigation data, surface hydrographic data
                    (salinity, temperature, fluorescence, light transmission, and sea water flow
                    rate), meteorological data (wind speed, wind direction, air temperature,
                    barometric pressure, and solar irradiance) was collected with the MIDAS
                    system. The MIDAS system sampling rate is an average of every fifteen
                    seconds. This system uses a Sea-Bird Electronics' temperature sensor, and a Sea
                    Tech, Inc. fluorometer and transmissometer. The conductivity- temperature
                    meter on the MIDAS is calibrated annually at Sea-Bird Electronics.

                    4.2.5. Data Analysis

                    This section describes the various analyses used to present and identify
                    physically meaningful processes or conditions. These analyses that are
                    accepted as routine within the physical oceanographic community are not
                    described in detail.

                    4.2.5.1 XBT and CTD Data P

                    Raw XBT frequency data     were processed with an in-house conversion
                    program using Sparton's     drop rates (Sparton of Canada, 1992). The
                    processed XBT data are interpolated at 1 m steps using a program developed
                    at Scripps Institute of Oceanography (La Jolla, CA). The XBT data are
                    calibrated against CTD casts. Scatter plots were made of the CTD depth and
                    XBT depth difference (for the compared isotherm) versus XBT isotherm
                    depth (Singer, 1990). The first order empirical fit was y = 0.047x - 2.9. A
                    depth adjustment was made in the data to compensate for the fact that XBT
                    isotherms were shallower than CTD isotherms.

                    The CTD data was processed using Sea-Bird's Seasoft software. The following CTD
                    data processing steps were used:

                     1. DATCNV: Converts raw data to binary engineering units and stores data in
                       CNV files.
                     2. SPLIT: Splits the CNV files into upcast and downcast files.
                     3. WILDEDIT: Checks for and marks 'wild' data points.
                     4. FILTER. Filters data columns to produce zero phase time shifts.
                     5.ALIGNCTD: Aligns specific temperature, conductivity, and oxygen
                       measurements with their corresponding pressure measurements.
                     6. In-house program: Converts temp. to ITS-90 scale (UNESCO, 1991).
                     7. CELLTM: Removes conductivity cell thermal mass effects from conductivity
                       data.
                     8. LOOPEDIT: Marks the scan where CTD is moving less than the minimum
                       velocity or traveling backwards due to ship roll.
                     9. DERIVE: Computes dissolved oxygen and depth.
                     10. BINAVG: Averages the data into 1 m. depth bins.
                     11. DERIVE: Computes salinity (PSS-78), density (EOS80), potential temperature
                       (Pot.Temp), specific volume anomaly (SVA), & sound velocity (Chen-

                                                                                                    83

                        Millero) using Fofonoff and Millard's (1983) formulas. Also computes
                        dynamic height anomaly (Dyn Ht).

                     The CTD salinity calibration data were obtained from upcast salinity water
                     samples and from temperature and salinity sensor calibration. These sensors
                     were sent to Sea-Bird Electronics, Inc. for calibration after 100 casts. Salinity
                     samples were analyzed in the Dept. of Oceanography of Texas A&M University,
                     using a Guildline Connectively Coupled Salinometer (model number 8400A). The
                     Salinometer was standardized with Wormley Standard Seawater. Salinity bottle
                     data were plotted against CTD salinity casts. Differences were found to be within
                     the range of the accuracy of the instruments.

                     4.2.5.2 MIDA

                     The MIDAS continuously recorded data was processed with. an in-house
                     program which cuts cruise track lines from the continuously recorded file,
                     and plots raw data with no corrections.

                     4.2.5.3 D=amic Hv,.j@

                     XBT data were combined with CTD data to compute local geostrophic circulation
                     fields. A micro VAX 3600 computer was used for the calculations of dynamic
                     height and mass transport/geostrophic velocity between station pairs, as
                     described by Biggs, et al. (1990). All of our geopotential computations for
                     cruises 1-4, and 6 are referenced to the 800 dbar surface (GulfCet cruise 5, is
                     referenced to the 500 dbar). Hofmannn and Worley (1986) have shown
                     empirically that choice of an 800 to 850 dbar reference level should allow
                     baroclinic transport calculations to be in the mass balance throughout the
                     western Gulf of Mexico. Their model is supported by transport calculations for
                     anticyclone eddies (Biggs, 1992).

                     4.2.6 Technical Discussion

                     4.2.6.1 Characteristic Temperature-Salinity RelationshiJ2

                     Figure 4.6 shows temperature versus salinity for all observations on cruises 2-
                     6. In addition, temperature-salinity (T-S) plots have been done for each of the
                     four seasons as follows: winter refers to December-january-February, and
                     incorporates Cruise 4 (Figure 4.7); spring refers to March-April-May, and
                     incorporates Cruises 1 and 5 (Figure 4-8); summer refers to June-july-August,
                     and incorporates Cruises 2 and 6 (Figure 4.9); and fall refers to September-
                     October-November, and incorporates Cruise 3 (Figure 4.10). These plots show a
                     remarkable uniformity below 17C, indicating that the waters in the study
                     area constitute essentially a single system. Data from all the hydrographic
                     stations reveals a distinct maximum salinity greater than 36.60 psu and a
                     minimum salinity less than 34.9 psu; this excludes the surface fresh water
                     near the Mississippi plume (which was as low as 12.76 psu).

                     These salinity signatures are characteristic of Subtropical Underwater and
                     Antarctic Intermediate Water, respectively. Usually the Subtropical
                     Underwater salinity maximum is centered at about 200 m. The Antarctic
                     Intermediate Water salinity minimum in the eastern Gulf occurs between
                     depth of 800 to 1000 in (shallower in the western Gulf). The intense salinity

                                                                                                                                                                                                                                      84

                                                                                                                 All TS Data: GulfCat Cruises 2-6
                                                                        35
                                                                                                                                                                                  U2-6.dat

                                                                                    ...................                                  .... . .... ...........
                                                                        30                             ................................. .                                                               .............

                                                                                                                                                                                              A

                                                                        25      . .........................................   --------- - ---- - ---- ....................... ... .....                   ...........

                                                                        20      . ...................  .....................  --- - ---------------- ..................... ................ . .. . ............
                                                       ch

                                                       CD
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                                                       E                15
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                                                                                                     .................. . ..............................................  .....................    .................

                                                                           5    . ........... . ...... ....... . ............                        ..................... .....................

                                                                           0
                                                                             10                    15                     20                     25                   30                     35                     40
                                                                                                                                    Salinity (PSU)

                                            Figure 4.6. T-S Plot: all C`TD data Cruises 2-6.

                                    30.000                                                                                                  CP

                                   20.000                                                  ...... ...... ..... .
                                                                                                           .. ...... .
                                                                                                                       I ..... .....

                                13
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                                                                  salinity (PSS-78 (PSU)                            2

                                                          Gulfcet Cruise 04 - All Stations

                             Figure 4.7. Winter T-S Plot: CTD data Cruise 4.

                                                                                                                                                     86

                                     30.000

                                                                                                                      A

                                 ct2o.000     . ...... ...... ......   ..... ...... ...... ..... ...... ...... ...              ............ .
                                                                                                                                                   0
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                                     0.0281-
                                              000                 25.000                  30.000                   35.000                  40.000
                                                                     salinity (PSS-78 [PSUH: 2

                                                     Spring Cruises (01 and 05)

                              Figure 4.8. Spring T-S Plot: CTD data Cruises 1 & S.

                                                                                                                                                                    87

                                                                                          Summer Cruises (02 & 06)
                                                         35
                                                                                                                             i'surnmer.dat'

                                                               . ......................................... ..                           . . . .............
                                                         30                                    ..........

                                                         25    . ............................................................... ..................... ..... . ..............

                                                         20    . ................... .....................  ..................... ..................... .....................  .........

                                             C,D

                                             E           15    . ................................................................
                                                                                                             .................. . ............................  ..............

                                                         10    . .............................                     *"*"'*'*"":"",*11,111111*11,-,* . ............

                                                           5   . ............. . .. ...................... ......... . .......... ..................... .................... ...................

                                                            0
                                                             10             15              20             25              30             35              40
                                                                                                   Salinity (PSU)

                                     Figure 4.9. Summer T-S Plot: CTD data Cruises 2 & 6.

                                                                                                                                                           88

                                                              p

                                     30.000

                                                                                                                                                         10

                                    20. 000    . ........ ...... ......  ..... ...... ...... ........... ...... ...... ....... .... ..... ...... .

                                 m

                                 ap

                                 c
                                                                                                                                                       101,

                                 OL

                                 IQ

                                    10.000    . . ...... ..... ......   ..... ..... ...... ............. ..... ...... ...... ..... ...... ...... ..

                                     0.
                                        OS8.000                    25.000                    30.000                   35.000-                  40.000
                                                                       salinity (PSS-78 (PSUI); 2

                                                              Gulfcet Cruise 03                          All Stations

                               Figure 4. 10. Fall T-S Plot: CTD data Cruise 3.

                                                                                                      89

                                                       All Data from T-I 0 XBTs
                                    0

                                  50

                                100

                                150
                          CL

                                200

                                250

                                300
                                    10         15         20          25          30         35
                                                       Temperature (deg. C)

                      Figure 4.11. T-10 XBT Temperature Plot: Cruises 1- 6.

                                                                                                                                                               90

                                                                                            All T-7 XBTS
                                                   0

                                               200     . ................
                                                                   ..................                      . ................ ................. . ...............

                                                       . ............... ........              . ................L................. .................  ................
                                               400

                                     E

                                     CL                                 0

                                               600     . ................
                                                                                  ................ ...... . ......... ..................C.................  ................

                                               Soo     . ................ ............. . ..................  .................. ...................
                                                                                                                          .................  ...............

                                              1000
                                                      0            5           10            15           20           25           30            35
                                                                                     Temperature (deg. C)

                               Figure 4.12. T-7 XBT Temperature Plot: Cruises 1- 6.

                                                                                            91

                                                    All Data from T-20 XBTs
                                  0

                               200

                               400

                         E

                         CL
                         4)

                               600

                               800

                               1000
                                   0     5      10    15     20     25    30     35     40
                                                     Tempemture (deg. C)

                    Figure 4.13. T-20 XBT Temperature Plot: Cruises 1- 6.

                                                                                                   92

                    maximum of the Subtropical Underwater is found in the region of the Loop
                    Current and in rings derived from this current. During the GulfCet cruises, we
                    have detected several eddies with a salinity greater than 36.60 psu, which is
                    the hallmark of Loop Current eddies.

                    XBT temperature data has been plotted by probe type: T-10 probe data are
                    represented in Figure 4.11, Figure 4.12 shows T-7 probe data, and T-20 probe
                    data are shown in Figure 4.13. These XBT data have not been corrected with the
                    depth adjustment which would have compensated for the XBT isotherms being
                    shallower than the CTD isotherms. These temperature versus depth plots show
                    the ranges of the variability in the XBT temperature profiles during cruises 1
                    to 6 cruises (1992-93). The presence of "bad" probes was also identified in this
                    fashion.

                    4.2.6.2 200C. 150C. and 8'C Isotherms

                    All XBT temperature data (XBT stations and extra XBT's) have been corrected
                    and plotted with CTD temperature data. Figures 4.14 through 4.32 show the 20',
                    15', and 8' C isotherm depths over the entire study area for cruises 1- 6.

                    The observed depth of the 15*C and 20*C isotherms, as well as the flat nature of
                    the 20*C isotherm, indicates the presence of features such as the eddy Triton in
                    Cruise 2, eddy "U" in Cruise 2, eddy N" in Cruises 3 and 4, and Eddy Whopper in
                    Cruise 6. Regions where the temperature surface is deep corresponds to
                    anticyclonic (clockwise) circulation, and those regions where the temperature
                    surface is shallow corresponds to cyclonic (counterclockwise) circulation.
                    Surface waters warmer than 14*C in the western Gulf are frequently
                    relatively flat in cyclonic eddies and do not always depict these features well.

                    A prominent anticyclonic eddy is almost always present in the western Gulf of
                    Mexico. Small cyclonic eddies (cold water) are often associated with the
                    periphery of this dominant feature, and the 8'C isotherm topography is the
                    preferred detection tool for these eddies. In particular, doming isotherms may
                    represent the initial stages of development of a cyclonic feature which is
                    linked to the primary eddy and evolves in strength during subsequent stages
                    of eddy-slope interaction. This intensification of the anticyclonic-cyclonic
                    pair (oppositely rotating vortices) has been observed in the past in the
                    western Gulf (Merrell and Morrison, 1981; Brooks and Legeckis, 1982; Merrell
                    and Vazquez, 1983; Broks, 1984). A comparison between the 15' and 8*C
                    isotherms can reveal different sizes and areas of eddy location that can
                    indicate whether the vertical axis of the core is tilted.

                    The following summary identifies the major hydrographic features found in
                    cruises 1 through 6 located by survey track (transect) lines (see Figure 4.4 for
                    track-line designations):

                    Cruise 1: Cyclonic eddy on track-line 7, (Figure 4.14, 4.15, and 4.16)

                    Cruise 2: Anticyclonic eddy, Triton, on track-lines 2 & 3 with associated strong
                               cyclonic eddy on track-line 5 (seen in the 15* and 8'C isotherm);
                               anticyclonic eddy "U", track-line 8 with associated cyclonic eddy on
                               track-line 11 (Figures 4.17 to 4.19).

                                                             Depth of 8 OC Isotherm (m)

                                                                                 GulfCet 01
                             --3        -96.5    -95.5      -94.5     -93.5
                           la. 0    30.5                                         -92.5     -91.5      -90.5     -89.5      -88.5
                             00                     1         1          1         1          1         1          1
                             0
                             OQ

                                    29.5
                           ()0
                           P. "
                           (D (D

                             00
                               0    28.5

                             0
                                    27.5                                                           WO            4%
                                                                                                  an.@

                             0

                             W

                                    26.5

                             Cr
                             P

                                    25.5
                             0

                                    24.5
                                        -96.5    -95.5      -94.5     -93.5      -92.5     -91.5      -90.5      -89.5     -88.1

                                          M
                                          CFQ
                                                                                           Depth of 15 'C Isotherm (M)

                                                                                                                              GulfCet 01
                                                         -96.5            -95.5            -94.5            -93.5             -92.5            -91.5            -90.5            -89.5             -88.5
                                                     30.5
                                          0
                                          CrQ

                                                     29.5

                                                                                                                                                                                                   4P

                                          Qn
                                             0
                                                     28.5

                                          CD                                                                                                                             Iva
                                          0                                                                                                      1-1

                                                                                                                 aft
                                                                                                                                                    aft
                                                     27.5                         no

                                                                                                    an

                                          W                                                                                                     1#
                                          0
                                          4W         26.5
                                          n
                                          M

                                          0          25.5

                                          X
                                          H          24.5
                                                            _96.5          -95.5             -94.5            -93.5            -92.5            -91.5            -90.5            -89.5             -88.5

                            PTI
                            OQ
                            CD                              Depth of 20 'C Isotherm (m)

                                                                                  GulfCet 01
                           0.0         -96.5     -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5      -88.5
                           0       30.5
                            0
                            (JQ
                          t:v "
                            so

                            0      29.5

                            (D

                            0
                              0    28.5
                            C)

                                   27.5

                                                          40

                                   26.5
                            r)
                            (D

                            (D
                            0.     25.5
                            0

                            X
                                   24.5
                                       -96.5     -95.5      -94.5      -93.5      -92.5      -91.5      -90.5      -89.5      -88.5

                           071
                           QQ
                                                           Depth of 8 OC isotherm (m)
                           CD

                           .4                                                  GulfCet 02
                           H         -96.5     -95.5     -94.5      -93.5     -92.5      -91.5     -90.5      -89.5      -88.5
                         CL 0    30.5
                           10
                           0
                           QQ
                          0

                                 29.5
                          00

                           0
                           0'0'  28.5

                                                   GOB
                                 27.5              on's

                           Gn

                                 26.5

                           CD
                           CL    25.5
                           0

                           X     2 4.5
                           to
                             3       -96.5     -95.5     -94.5      -93.5     -92.5      -91.5     -90.5      -89.5      -88.5

                                                                                                                        Depth of 15 0 Isotherm (m)
                                                 (D

                                                                                                                                                    GulfCet 02
                                                 -q                   -96.5              -95.5                 -94.5              -93.5                -92.5               -91.5                -90.5               -89.5                -88.5
                                                 0            30.5
                                                 ,a
                                                 .0

                                                              29.5
                                            C) 0

                                            CD   (D

                                                 LA           28.5

                                                 M

                                                                                                 "0.0

                                                 (D
                                                              27.5 -
                                                                                                 240.0                %
                                                                                                 280.0

                                                                                                                        -0
                                                 (D
                                                                                                 'P.0

                                                              26.5

                                                 0

                                                 CD
                                                 Q.           25.5
                                                 0

                                                              24.5
                                                                      -96.5              -95.5                -94.5               -93.5               -92.5                -91.5               -90.5                -89.5                -88.5

                            ql
                            QQ
                                                                Depth of 20 0 Isotherm (m)

                                                                               GulfCet 02
                                     -96.5      -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5      -88.5
                          ao
                            @O    30.5                                  -T -

                                  29.5
                            0

                         (D (D

                             0    28.5

                                  27.5                                                                        jODA

                                  26.5
                                                                            oto
                            r)

                            CD
                            a     25.5
                            0

                            X
                                  24.5
                                     -96.5      -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5      -88.5

                           CrQ
                           0                                Depth of 8 'C Isotherm (m)

                                                                                GulfCet 03
                                     -96.5      -95.5     -94.5
                         0.0      30.5                               -93.5      -92.5     -91.5      -90.5      -89.5      -88.5
                         n'O                       I I I- I I
                         .qO                                                                            I

                                  29.5

                         C4
                           CD

                           0,
                             0
                                  28.5

                                  27.5

                                  26.5

                                  25.5

                                  24.5
                                     -96.5      -95.5      -94.5     -93.5      -92.5      -91.5     -90.5      -89.5      -88.5

                                        (IQ
                                                                                               Depth of 15                                 Isotherm (m)

                                                                                                                      GulfCet 03
                                    a 0                 -96.5          -95.5           -94.5            -93.5            -92.5           -91.5            -90.5            -89.5           -88.5
                                        10        30.5
                                        A

                                                  29.5
                                     ()0

                                    M M

                                        LA
                                           0      28.5
                                        n

                                        r-t
                                        M

                                        M
                                                  27.5                        240:
                                                                                                 'tbo                           240A

                                                                              "0.0
                                        M
                                        W
                                        r.
                                        04        26.5
                                        r)                                      b
                                        (D
                                        cr

                                                  25.5
                                        0

                                        X
                                                  2 4.5
                                                        -96.5          -95.5            -94.5            -93.5           -92.5            -91.5           -90.5            -89.5            -88.5

                             OTI
                             OQ
                                                                   Depth of 20 0 Isotherm (m)

                                                                                   GulfCet 03
                          CL 0          -96.5     -95.5      -94.5       -93.5      -92.5      -91.5       -90.5      -89.5       -88.5
                             10     30.5
                             .0

                          C) 0      29.5
                          P  "
                          '.

                                                                                                                               o
                                                                                                                               9

                               0    28.5

                                                                                   --------------

                             M
                                    27.5

                                                       Oop
                                    26.5

                             M

                             (D
                             P.     25.5
                             0

                             X
                             tz     24.5 1
                               3        -96.5     -95.5       -94.5      -93.5       -92.5      -91.5      -90.5       -89.5      -88.5

                           OQ
                                                           Depth of 8 . OC Isotherm (m)

                                                                               GulfCet 04
                                     -96.5     -95.5      -94.5     -93.5      -92.5     -91.5      -90.5     -89.5      -88.5
                           8'    30.5
                           10
                           0

                                 29.5
                           0

                                                                                                                      P
                           0*0   2 8.5
                           n

                           P-t
                           CD                                                                  -A,
                           El

                                 27.5

                           CA
                           0
                                 26.5

                           (D

                           cr

                           CD
                           Q.    25.5
                           0

                           X
                           tz    2 4.5
                                     -96.5     -95.5      -94.5     -93.5      -92.5     -91.5      -90.5     -89.5      -88.5

                                                              Depth of 15 'C Isotherm (m)

                                                                                     GulfCet 04
                          la. 0
                                       -96.5       -95.5      -94.5       -93.5      -92.5       -91.5      -90.5       -89.5       -88.5
                                    30.5

                          CL

                          C) 0
                              "     29.5

                                    28.5

                                    27.5
                                                       SIP
                              CD

                                    26.5
                              M

                                    25.5

                                    24.5
                                         -96.5     -95.5       -94.5      -93.5       -92.5      -91.5       -90.5       -89.5      -88.5

                                        OQ
                                                                                               Depth of 20 0 Isotherm (m)

                                        @A                                                                           GulfCet 04
                                        -q              -96.5          -95.5           -94.5           -93.5            -92.5           -91.5           -90.5            -89.5           -88.5
                                    CL 0
                                        10        30.5
                                        MO

                                                  29.5
                                    n 0

                                    M   (D                                                                                                                                         40.0
                                        w                                                                                                                                     . 00,
                                        0         28.5

                                                                                      boo
                                                                              logo
                                        M                                     io@        Z::@@                                                                                        -No
                                                  27.5                         oj:

                                                                                                                                                       fto

                                                  26.5

                                        CD
                                        cr
                                        P)
                                        co
                                        CD
                                        la,       25.5
                                        0

                                        X
                                        w         24.5
                                           3            -96.5          -95.5           -94.5            -93.5           -92.5           -91.5            -90.5           -89.5           -88.5

             tn

                               LSU Earth Scan Lab

                               Coastal Studies Institute

                               NOAA-11 SST

                               12 FEB 1993 100OZ

                                                               iii:- S,
                                                                            Rx. W, A

                                                                                 ft

                                                                                 . . . . . . . . . . . .

                           CIQ
                                                           Depth of 8 'C Isotherm (m)

                             4                                                GulfCet 05
                           -3    30.5 96.5     -95.5     -94.5      -93.5     -92.5      -91.5     -90.5      -89.5     -88.5
                         0.0
                           00
                           0
                         UCIQ
                         0-0
                                 29.5

                           0
                           "h

                         @A 00   28.5 5
                             0

                           M
                           5

                                 27.5

                                 26.5
                           -Sol)

                           C4
                                 25.5

                           0

                           X     24.5
                                    -96.5      -95.5     -94.5      -93.5     -92.5     -91.5      -90.5     -89.5      -88.5

                             OQ
                                                              Depth of 15 OC Isotherm (m)
                             4@1
                             ili
                             90                                                      CulfCet 05
                                        -96.5      -95.5      -94.5       -93.5      -92.5       -91.5
                          P. 0                                                                              -90.5       -89.5      -88.5
                             00     30.5
                             =0

                                    29.5
                           no

                          (D M

                               0    28.5
                             n                                                                                                        %
                             -f
                             M
                             5
                             (D                                                                  4P
                                    27.5

                             CD

                                    26.5

                             M

                             M
                                    25.5
                             0

                             X
                                    2 4.5
                                        -96.5      -95.5       -94.5      -93.5       -92.5      -91.5       -90.5      -89.5       -88.5

                             OTI
                             ClQ
                                                             Depth of 20 OC Isotherm (m)

                             %10                                                    CulfCet 05
                             *-3      -96.5      -95.5       -94.5      -93.5       -92.5      -91.5      -90.5       -89.5      -88.5
                          CL 0     30.5
                             10
                             .0

                                   29.5
                          C) 0

                          (D M

                                   28.5
                              0

                             M
                             11    27.5

                             M

                                   26.5

                             ei
                             M
                             cr
                             ID
                             W
                             0
                             91    25.5
                             0

                             tz    2 4.5
                              3       -96.5      -95.5       -94.5      -93.5      -92.5       -91.5      -90.5       -89.5      -88.5

                            QQ
                                                               Depth of 8 OC Isotherm (m)
                            (D

                                                                                    GulfCet 06
                            -*3        -96.5      -95.5      -94.5       -93.5      -92.5       -91.5      -90.5       -89.5      -88.5
                         1110      30.5              1
                         Q
                            ,a
                            0

                         P         29.5
                         no

                            (D

                            00
                             0     28.5
                            C)

                            CD

                            CD                                                           6"A          MA
                                   27.5

                                                                                 s2xo

                                   26.5

                            CA
                            CD
                            0.     25.5
                            0

                            X
                            W      24.5
                             3         -96.5      -95.5      -94.5       -93.5      -92.5       -91.5      -90.5       -89.5       -88.5

                                1

                            :M
                            QQ
                                                                   Depth of 15 OC Isotherm

                                                                            GulfCet Cruise 06
                                        -96.5     -95.5      -94.5       -93.5      -92.5      -91.5       -90.5      -89.5       -88.5
                            0      30.5
                          M@O
                          ._30
                            CIQ

                          no       29.5

                          (D
                                                                                                                                     C,
                            U1
                              0    28.5
                                                                                                                   -,JOB ODA

                            (D
                            5

                                   27.5

                                   26.5

                            (D
                            cr

                                   25.5
                            0

                            X
                            W      24.5
                              3         -96.5     -95.5       -94.5      -93.5      -92.5       -91.5      -90.5      -89.5       -88.5

                       OQ                                     Depth of 20 OC Isotherm

                                                                      GulfCet Cruise 06
                                 30.5 96.5    -95.5       -94.5    -93.5      -92.5     -91.5     -90.5      -89.5      -88.5
                    CL 0

                                 29.5

                    c') 0

                    M  0
                                                                                                                          Sub
                    P            28.5
                        0
                       n

                       (D                                     Otto
                                                       to" ----
                                                               I   \J
                                 27.5
                                                  lies
                                                              -     I%*

                                 26.5

                       CA
                                 25.5

                       0

                       X         2 4.5
                       W            -96.5     -95.5       -94.5    -93.5      -92.5     -91.5      -90.5     -89.5      -88.5

                                                                                                    112

                     Cruise 3: Anticyclonic eddy on track-lines 2 & 3, eddy "V", detected at all three
                                isotherm depths (Figures 4.20 through 4.22).

                     Cruise 4: Anticyclonic eddy on track-lines 2 & 3, eddy "V"; cyclonic eddy on
                                track-lines 9 & 10 (evident on Figure 4.23) associated with
                                anticyclonic eddy found on track-line 12, not named, but confirmed
                                by satellite image (Figures 4.24 through 4.26).

                     Cruise 5: Very complex topography, presence of small weak cyclonic eddies at
                                the southern border (Figure 4.27) and small anticyclonic eddies
                                inside our study area (Figures 4.28-4.29).

                     Cruise 6:  The anticyclonic eddy "W" on track-lines 4, 5, and 6; eddy "W' is
                                elongated and squashed with an associated cyclonic eddy on track-
                                line 7. Anticyclonic eddy " X" or the Loop Current, on track-line 12
                                (Figures 4.30 through 4.32).

                     4.2.6.3 Dynamic Height

                     Eddy Triton was not present in the western Gulf during Cruise 1, April, 1992
                     (Figure 4.33). It was seen on Cruise 2, August, 1992, with a dynamic height
                     greater than 125 dyn cm and salinity greater than 36.6 psu (Figure 4.34).
                     During the same summer cruise, eddy "U", in the central area of our study,
                     presented a dynamic height greater than 140 dyn cm. Figure 4.35 is a
                     composite figure of dynamic heights and LATEX A drifter track number 2447
                     for the month of August, 1992. Eddy "V" was detected on our fall (November
                     1992) with a dynamic height greater than 140 dyn cm (Figure 4.36), and in the
                     winter cruise (February 1993) with a dynamic height around 125 dyn cm
                     (Figure 4.37). Figure 4.38 is a composite figure of dynamic heights and LATEX A
                     drifter track number 2447 for the month of November 1992. The complex
                     topography seen in the spring Cruise 5 did not present any dynamic features
                     (Figure 4.39). Cruise 6, on August 1993, detected the north side of eddy "W" with
                     � dynamic height around 120 dyn cm, and eddy "X" (or the Loop Current) with
                     � dynamic height higher than 145 dyn cm (Figure 4.40).

                     4.2.6.4 Cloroj2hyll Dat

                     Chlorophyll analyses are still underway, with only preliminary results
                     presented here. Figures 4.41 through 4.44 show the surface chlorophyll a
                     values determined for cruises 3 to 6. Surface values range from 0.01 to 0.18
                     Mg/M3, with higher values found in the area near the Mississippi River
                     plume. "Hotspots" of chlorophyll are seen offshore in Cruises 3 and 5. Further
                     analyses will attempt to correlate these hotspots: with the cold cyclonic eddy
                     seen in the 8'C isotherm depth maps.

                     4.2.6.5 Mississippi River: 1992 versus 1993

                     Figures 4.45 through 4.50 show salinity versus 0, 3, and 5 m depths for cruises
                     2 and 6. During the 1993 flood, the Mississippi plume was streaming to the east,
                     which is a rare occurrence. This event is shown in satellite images (Figure
                     4.5 1) and confirmed by our hydrographic data.

                                                  Surface Dynamic Height (dyn cm.)
                           CD

                                                                               GulfCet 01
                                     -96.5     -95.5      -94.5      -93.5     -92.5      -91.5     -90.5      -89.5      -88.5
                                  30.5

                           (D

                                  29.5

                           0
                           @o
                           0      28.5
                           (JQ

                           :r

                                  27.5

                                  26.5

                           0
                           00     25.5

                                  24.5
                                     -96.5     -95.5      -94.5      -93.5     -92.5      -91.5      -90.5     -89.5      -88.5

                                                   :ii
                                                                                                 Surface Dynamic Height (dyn. cm)
                                                   CD
                                                   -P,
                                                                                                                                                             GuIfCet 02
                                                   C/)                -96.5                 -95.5                 -94.5                -93.5                 -92.5                 -91.5                -90.5                  -89.5                -88.5
                                                                30.5

                                                   r)
                                                   CD

                                                                29.5

                                                   r)
                                                   f-t
                                                   0

                                                   0
                                                   OQ           28.5

                                                                                                                                                                                                            fee
                                                                27.5

                                                                                                                   kb

                                                                26.5                                                                              %dl

                                                                                                                                           Ila
                                                   M
                                                   r)

                                                   0
                                                                25.5

                                                                24.5
                                                                      -96.5                 -95.5                 -94.5                -93.5                 -92.5                 -91.5                -90.5                  -89.5                -88.5

                              CrQ                        Surface Dynamic Height (dyn cm.)
                              (D

                              4
                                                                                       GulfCet 02
                                               30.5 96.5   -95.5     -94.5    -93.5     -92.5    -91.5     -90.5     -89.5    -88.5     -87

                              CD               29.5

                            -40

                                               28.5

                           0 (D
                           QO

                                               27.5
                                                                                                                             3MU

                                                                                                                                    lag

                              0
                              10               26.5
                              0                                                lag       40
                              QQ

                                                                                                                                           is
                              @3'              25.5                                          31
                                                                                             jol

                              r)
                                                                                                                                      240
                                               24.5                                                 "MR     SAMI

                                               23.5

                                               22.5
                                                  -96.5     -95.5    -94.5     -93.5    -92.5     -91.5    -90.5     -89.5    -88.5     -87

                            @V
                            aQ
                                                               Surface Dynamic Height

                            ON                                          GulfCet Cruise 03
                                     -96.5      -95.5      -94.5     -93.5      -92.5      -91.5      -90.5      -89.5      -88.5
                                   30.5

                          CD
                            M

                                   29.5

                            0
                            11:3
                            0
                            (IQ    28.5

                                   27.5

                                                                 14

                                    26.5
                            CA

                            (D

                            0
                            00      25.5
                            0
                            0

                            0       24.5
                            4          -96.5     -95.5      -94.5     -93.5      -92.5      -91.5      -90.5      -89.5      -88.5

                           OQ
                                                              Surface Dynamic Height

                             4
                                                                       GulfCet Cruise 04
                                      -96.5    -95.5      -94.5     -93.5      -92.5      -91.5     -90.5      -89.5      -88.5
                                  30.5
                                                                                -F-

                                  29.5

                           0
                           10
                           0
                                  28.5

                                  27.5              lap

                                                                       fto

                                  26.5

                           0

                           0
                           00     25.5
                           0
                           0

                           0      24.5
                           5          -96.5    -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5     -88.5

                            GQ
                                                   Surface Dynamic Height (dyn cm.)

                                                                                GulfCet 03
                            po       -96.5      -95.5      -94.5     -93.5      -92.5     -91.5      -90.5      -89.5      -88.5
                                  30.5

                                  29.5

                                  28.5

                                                                                                                           lam

                            0     27.5
                            10
                            0

                                                                           Ilu
                                  26.5

                                  25.5

                                  24.5
                                     -96.5      -95.5     -94.5      -93,5      -92.5     -91.5      -90.5      -89.5      -88.5

                                    Dynamic Height (dyn. cm)

                                               CulfCet 05
                C: V)  -96.5       -94.5       -92.5
                     30.5                                   -90.5       -88.5

                 (D

                 r)

                 0
                 10
                 0   28.5

                     26.5
                 CD
                 W

                 (D

                 0
                 00

                 0   24.5
                 51    -96.5       -94.5       -92.5        -90.5       -88.5

                                                  Surface Dynamic Height (dyn cm.)
                           CD

                                                                               GulfCet 06
                         r. Cn        -96.5    -95.5      -94.5     -93.5      -92.5      -91.5     -90.5      -89.5      -88.5
                           r      30.5

                           r)
                         ON M

                         M        29.5

                           0
                           0      28.5
                           OQ

                                                                                               NO
                                  27.5

                                                                                     %lob
                                                                                   lisp Ina
                                  26.5                                      a

                           00     25.5
                           C)
                           0

                                  24.5
                                      -96.5    -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5     -88.5

                                     QrQ
                                     (D                                                 Surface Chia. (mg/m 3)
                                  Z                                                                             GulfCet 03
                                  0                -96.5                         -94.5                          -92.5                         -90.5                          -88.5
                                  CD          30.5

                                     0
                                  CD "
                                     0

                                     JID
                                                                                                                                                                                  4@p

                                  CD
                                               28.5
                                  r) r)
                                     (D                                                                                                                                       0.25
                                  0  -                                                                                                        op ,p
                                  on* 0,                                                                                                           ,P

                                  UJ
                                                                                           0.25                                    Q'Yo
                                                                                                                     0

                                               26.5

                                     OQ

                                     GQ

                                                2 4.5
                                     (D             -96.5                          -94.5                         -92.5                          -90.5                          -88.5
                                            1

                                                               Surface Chia. (mg/m 3)

                                                                               GulfCet 04
                                     -96.5                -94.5                -92.5                -90.5                -88.5
                                  30.5

                                  28.5

                                                                                             0.50
                                  26.5

                           QQ
                           1-1

                           @31    24.5
                           (D        -96.5                -94.5                -92.5                -90.5                -88.5

                                                                         Surface Chla. (mg/m 3)

                                                                                             GulfCet 05
                            1,0            -96.5                    -94.5                    -92.5                   -90.5                     -88.5
                                       30.5
                                                                      T-

                                       28.5
                                                                                                                                           @,I. 2 2
                                                                                                                                               0.14
                                                                                                                         o
                                                                                                                          V

                                                                    ---o.i    4
                                                                                                                          1.00
                                                                                                                          I

                               (FQ
                               1@1     26.5

                                Ui
                                                                                                                                               qp

                               GQ

                               M

                                       24.5
                                           -96.5
                                                                    -94.5                    -92.5                    -90.5                    -88.5

                         QQ
                                                          Surface Chla. (mg/m 3)

                                                                         GulfCet 06
                                   -96.5              -94.5              -92.5               -90.5              -88.5
                                30.5

                         0

                       Uj
                       CA

                       CD
                                                                                                                 CV

                                28.5

                       rA
                       rD                                                                   0.0
                                                                                  CIL0.0

                                26.5

                         OQ

                         QQ
                                24.5 -
                         :31
                         M         -96.5              -94.5               -92.5              -90.5               -88.5

                                                               Surface Salinity (PSU)

                                                                        GuIfCet Cruise 02
                         n           -96.5     -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5     -88.5
                                  30.5                                   -                                      --

                            gal
                                  29.5

                            0
                                  28.5

                                                                                   4to                               3&0

                                  27.5
                                                                                       @3&0

                            QQ

                            :3'
                            (D
                                  26.5

                            CrQ

                                  25.5

                                  24.5
                             D
                                     -96.5     -95.5      -94.5      -93.5     -92.5      -91.5      -90.5      -89.5      -88.5

                                             M
                                             CIQ
                                             (D                                                       CTD Salinity at 3m (PSU)

                                                                                                                                       GuIfCet 02
                                                             -96.5                                -94.5                                -92.5                                -90.5                                 -88.5
                                                         30.5

                                          Nq

                                             0
                                             0
                                                         28.5

                                             uj
                                             EI
                                             CL

                                             OQ

                                                          26.5

                                             QQ

                                             cn

                                                          24.5                                                                                                               -90.5                                 -88.5
                                                                _96.5                              -94.5                                -92.5

                                                                       CTD Salinity at 5m (PSU)

                                   4
                               0                                                               GulfCet 02
                                           -96.5                     -94.5                     -92.5                     -90.5                     -88.5
                                       30.5
                              (D ".                         I            I            I           I            I            I             I            I

                                        28.5

                                 crQ

                                 't
                                 @31
                                 (D
                                 >      26.5
                                 r_
                                 OQ

                                 CD
                                        24.5
                                            -96.5                     -94.5                     -92.5                     -90.5                     -88.5

                                                               Surface Salinity (PSU

                                                                        GuIfCet Cruise 06
                         C4          -96.5      -95.5      -94.5     -93.5      -92.5     -91.5      -90.5      -89.5      -88.5
                                   30.5

                                   29.5

                                   28.5

                                   27.5

                         UQ

                         (D        26.5

                         CrQ
                         0

                                   25.5

                         CA

                         (D        2 4.5
                                       -96.5    -95.5      -94.5      -93.5      -92.5     -91.5      -90.5      -89.5     -88.5

                          (IQ
                                                        CTD Salinity at 3m (PSU)

                                                                          GuIfCet 06
                                  -96.5               -94.5               -92.5               -90.5               -88.5
                                30.5

                          CO)

                          0

                                28.5

                          >     26.5
                          V.
                          OQ
                          0
                          CA

                                 2 4.5
                                    -96.5               -94.5              -92.5               -90.5                -88.5

                                            Oil
                                                                                                    CTD Saiinity at 5m (PSU)

                                                                                                                                      GulfCet 06
                                                            -96.5                                -94.5                               -92.5                                -90.5                                -88.5
                                                       30.5

                                                       28.5                                                                                                                                    34.5
                                            L,n                                                                                                                                         35@5

                                                                                                                                          ip

                                                                                                                                                                 35-5
                                            QQ

                                            (D         26.5

                                            QQ
                                            r_
                                            co)

                                            I.-
                                            %Z

                                                       24.5
                                                            -96.5                                -94.5                               -92.5                                -90.5                                -88.5

                                                                                             131

                                                                      to

                                                                           4

                                                                        It

                                                                 S.,0

                  Figure 4.5 1. NOAA-AVHRR    reflectance analysis in the   western Gulf of
                              Me@dco for August 10, 1993 (Coastal Studies Institute).

    132
    4.3.7 Conclusion
    Our sampling grid has proven to be useful in sampling the meso-to-large scale features of the gulf of Mexico. We were able to detect all the major eddies and events present in the northwestern Gulf from 1992 to 1993. These anticyclonic eddies shed vorticity as regions of cyclonic circulation when they feel bottom, and the companion cold-core (upwelling) features probably are areas of greater production and may be preferred areas for marine mammals. Further analyses on the hydrographic features and environmentl habitat of marine mammals continues.
    4.3 remote Sensing and Geogrphic Information System
    4.3.1 Introduction
    Oceanographic observations obtained from satellites have some important advantaged (but also limitations) over observations obtained from ship. The first advantage is synopticity, or the ability to have an overall view of a large part of the ocean in a short time. The capacity of satellite sensors to sample large areas of the ocean densely and rapidly has imporoved greatly our ability to observe spatial patterns and patchiness. The assessment of heterogeneity and identification of spatial structure provide important information regarding physical and biological oceanography, especially as marine organisms are known to have a nonuniform distribution (Steele, 1978).
    Stennis Space center (NMFS) is providing remote sensing and geographic information system (GIS) support for the GulfCet project. The GIS will be used to integrate and analyze the various data types to explore possible relationships between the distribution and abundance of marine mammals and satellite and shipboard measurements of environmental variables in the Gulf of Mexico.
    4.3.2 Tasks Completed
    4.3.2.1 Support for Ship and Aircraft Surveys
    The acquisition of satellite images continued in an effort to support the ship and aircraft surveys during the two year field effort. The data are collected by the Advanced Very High Resolution radiometer (AVHRR) carried onboard the NOAA polar orbiting satellites and provide partial or full coverage of the study area twice per day (one daytime and one nighttime overflight) depending on thge orbital path and cloud coverage. The data are durrently being obtained from the NOAA-11 satellitte and are expected to be available from NOAA-12 in the near future. With both satellites operating, up to four images per day will be available. The Naval Research Laboratory at Stennis Space Center maintains a satellite receiving station and archive facility for AVHRR images and is the primary source of data for the project. The satellite data are being processed into sea surface temperature (SST) images. Figure 4.52 is an example of the product, using the multichannel SST algorithms described by McClain, et al. (1985), and rectified to fit a simple cylindrical (linear longitude/latitude) map projection (Snyder, 1987). Each SST image is also being processed into an

                                                                                                 133

                    Figure 4.52. NOAA-AVHRR SST analysis in the Gulf of Me)dco, April 11,
                                1993.

                                                                                                                                                                                          134

                                                                Daw         Time       , satellite   -28 Lit                  Date                                .2zhhL.
                                                             R2-A?R-92      CN?        HCAA- 12      13,226               12-NOV-92       09:59     MOAA-iR       22.305
                                                             U-A?a-92       U:04       WOAA-la       R8,293               22-FOV-92       2aM       N(DAA-1 a     21,s3g
                                                             13-APEZ-92     20.26      WCAA-lt       M305                 29-Hav-92       W:55      WCAA-a I      2a.546
                                                             14-APR-92      08:51      NCAA-1 I      Ra'=                 29-NOV-92       2R:19     MOAA-11       2R,553
                                                             RS-AM-92       03:39      HOAA-11       R2,326               30-NOV-92       0:43      FOAA4 2       Z,560
                                                             RS-AI?R-92     20:02      NOAA- L R     18,333               LO-NOV-92       22-05     NOAA-u        2E,567
                                                             L7-AM-92       21:19      MAA-la        a9,362
                                                             20-AM-92       09-.23     HOAA-11       M397                 W-DSC-92        09:23     HOAA-11       22,701
                                                             20@-ARR-92     2C:43      KOAA-RR       NAV                  Ra-DFZ-92       C9:RR     NCAA-la       22,7U
                                                             21-AI?R-92     09:00      NCAA-H        13,4E R              12-DEC-92       20:32     NOAA-1 a      22,722
                                                             2R-AM-92       20:30      HGAA-LI       19ARS
                                                             22-A?R-92      08:56      HOAA49        R8,425               U-JAN-93        09:23     NOAA-an       22,054
                                                             22-AM-92       20:29      WOAA-A@       L8,41                WAN-93          20:431    HCAA- 19      M,MB
                                                             23-AM-M        M:,M       NCAA-L 2      18,43P               23-JM-93        09:46     INOAA-A t     22,3'n
                                                             27-AM-M        W:Q        NOAA-ga       33,496               X-J"-9.3        W:58      WDAA-H        M.435
                                                             27-AM-M        *2R.C0     ?SOAA-12      N,50                 X-9AX-M         'a: t 1;  HOAA-11       22'@92
                                                             23-AM-M        20:42      kZOAA-9 @     N,527
                                                                                                                          M-nn-n          C9:02     WOAA-la       M,3,62
                                                             Q-MA'S-0.      M:49       MOAA-11       12,352               G&R&M           22M       NOAA-U        22.555
                                                             OR-MAY-92      20:12      WCAA-11       M559                 RE-FES43        2R:26     NOAA-H        22,593
                                                             02-WAY-92      03:37      FOAA-N        R@,566               M-FES-93        09:54     NOAA-la       22,605
                                                             M-MAY-92       20:CD      W0AA-R 9      99.5Z                M-FER-93        2R:IG     NOAA-H        22,GR2
                                                             CS-MAY-92      COM        NOAA-SR       R2,623               90-FEB-M        C9:42     NOAA-8 1      22,60
                                                             MMAY-92        20:51      MOAA-LI       19,WD                U-FES-91        21:02     W0AA- Z a     22,626
                                                             07-MAY-M       OP:R9      NCAA-R2       M,W?                 a?-FEB-93       20:E4     NGAA-1 a      22,622
                                                             O&MAY-92       20:2.2     9ZOAA-1 9     E8,658
                                                             W-MAY-92       MZ7        WOAA-at       98,672               0041AR-93       MIS       HGAA-H        =U7
                                                             20-MAY-92      20;03      NGAA-9 a      RSAW                 04-MM-0         2C:33     HOAA-ga       22'w
                                                             92-MAU-92      20:45      NOAA-H        M757                 CS-MAR-M        09-02     NOAA-la       =WE
                                                             a&MAV-92       CO:14      NCAA-R @      M764                 09-MU-93        20-.05    NCAA- a a     =W
                                                             W-MAY-K        WAS        NOAA- 19      M,M                  W-MU-N          09:53     NCAA-2 9      =953
                                                             RNMAIT-92      MSG        NOAA-RE       MORI                 09-bUR-93       22:23     NOAA-al       22,M
                                                             29-MAY-92      C9:54      NCAA-Ra       A'835                M-MM-M          09:Q      NCAA-la       22,972
                                                             2R-MAY-n       2W6        NOAA-9n       as'842               a"LAR-93        21-01     NOAA-H        22,M
                                                             25-MAY-92      C9.07      NCAA-RR       R8,SD2               %-@4M-93        20-W      NOAA-a L      23,RW
                                                                                                                          26-MM-0         09:46     NOAA-H        23,M
                                                             02-AUG-92      0@:56      N0AA-!H       25),W                27-MAR-M        09M       NOAA-ER       23,292
                                                             10-AUG-92      09:45      NOAA-99       20,249               29-MM-M         09.25     NOAA-H        22 =6
                                                             30-AU(M-92     &:05       NOAA-9 a      20,269               X-MAR-M         29:48     NOAA-RE       23,276
                                                             39-AUC-92      0:33       NOAA-19       2OX3
                                                                                                                          02-AM-M         20.95     KCAA-R2       2Z.=
                                                             M-SEP-92       0:0        NOAA-29       20=                  On-AFR-0        2a:36     NCAA-R 2      23,290
                                                             M-SEP-92       20:29      NGAA-R a      22,SRO               M-APR-0         ROM       HUAMR         23,297
                                                             M-SW-92        0@67       NGAA-H        20,M                 90-APR-0        LOW       HCAA-H        23,MO
                                                             H-SV-92        W:09       NOAA-2 E      20,430               M-AFR-N         29:27     NOAA-1 R      22.4R?
                                                             H-SSP-92       20.22      NOAA-19       2Z,417               U-AFR-M         09:34     NOAA-RR       23,424
                                                             EMEP-92        0:05       NOAA-aR       20,563               HAMM            29:23     NOAA-2 @      22,,M
                                                             U-Qw-n         20:U       NOAA-aa       MISSO                M-AM-M          W:"       NOAA-ag       23,,WS
                                                                                                                          22AM-N          22.W      NOAA-ta       23,445
                                                                            20:5 9     NCAA-H        20,762               n3-APR-M        20:30     NOAA-Eg       23,427
                                                             CS-OZT-92      MIS        NOAA-H        22,7W                Re-Amm          20:35     NOAA-u        23"695
                                                             03-C=-92       20:39      k30AA-RR      20@776               ng-APR-0        22:33     NOAA-S 1      23,530
                                                             M-CCT42        69:31      NOAA-92       23,85C               22-APR-93       09M       NCAA-H        22,579
                                                             n-=T-92        2wa        NaAA-aa       2axs                 22-APA-93       20:45     NOAA-E 3      239596
                                                             M-CZT-92       09:R9      NOAA-R D      20.882               23-MR-0         09:0 L    NOAA-B 2      23,593
                                                             as-=-92        20:39      FGAA-AR       20,829               26-APR-93       2a:34     NOAA-2 1      2Z,663
                                                             a4-CC7-92      CD-07      NOAA-H        20,896               27-AM-9.1       I"a       NOAA-Za       21,650
                                                             M-OCT-92       20:27      NOAA-82       23,M

                                   Table 4. 1. Date and                    time      (GMT) of acquisition, satellAte and orbit numbers of
                                                          the 106 AVHRR images acquired through October 2986.

                                                                                                                                                                   135

                                                   04-MAY-93     10:16    NOAA-11    23,749                  01-JUL-93     10:15    NOAA-11     24,568
                                                   04-MAY-93     21:40    NOAA-11    23,756                  01-JUL,93     21:39    NOAA-I 1    24,575
                                                   05-MAY-93     10:04    NOAA-11    23,763                  02-JUL-93     10:02    NOAA-11     24,582
                                                   06-MAY-93     09:52    NOAA-11    23,777                  02-JUL-93     21:25    NOAA-11     24,589
                                                   06-MAY-93     21:14    NOAA-11    23,784                  04-JUL,93     21:M     NOAA-11     24,617
                                                   07-MAY-93     09:39    NOAA-11    23.791                  05-JUL-93     09:24    NOAA-11     24,624
                                                   07-MAY-93     21:04    NOAA-11    23,798                  07-JUL-93     10:41    NOAA-11     24,653
                                                   09-MAY-93     09:25    NOAA-11    23,805                  09-JUL,93     10:30    NOAA-11     24,667
                                                   11-MAY-93     10:31    NOAA-11    23,848                  16-JUL-93     21:58    NOAA-11     24,797
                                                   12-MAY-93     10:19    NOAA-11    23,862                  17-JUL-93     21:44    NOAA-11     24,801
                                                   13-INUY-93    21:31    NOAA-11    23,883                  19-JUL-93     21:19    NOAA-11     24,829
                                                   14-MAY-93     09:55    NOAA-11    23,890                  25-JUL-93     21:47    NOAA-11     24,914
                                                   14-MAY-93     21:19    NOAA-11    239897                  26-JUL-93     10:12    NoAA-11     24,921
                                                   15-MAY-93     21:07    NOAA-11    23,911
                                                   16-MAY-93     09:28    NOAA-11    23,918                  01-AUG-93     01:16    NOAA-12     11,503
                                                   16-MAY-93     20:53    NOAA-11    23,925                  05-AUG-93     01:32    NOAA-12     11,560
                                                   17-MAY-93     09:16    NOAA-I 1   23,932                  07-AUG-93     00:47    NOAA-12     11,589
                                                   17-MAY-93     20:43    NOAA-11    23,939                  10-AUG-93     10:29    NOAA-11     25,133
                                                   18-MAY-93     09:04    NOAA-11    23,946                  18-AUG-93     21:57    NoAA.11     25,253
                                                   21-MAY-93     10:11    NOAA-11    23,989                  19-AUG-93     10:21    NOAA.11     25,260
                                                   21-MAY-93     21:34    NOAA-11    23,996                  19-AUG-93     13:49    NOAA-12     11,766
                                                   22-MAY-93     09:59    NOAA-11    24,003                  22-AUG-93     09:44    NOAA-11     25,302
                                                   23-MAY-93     09:46    NOAA-11    24,017                  22-AUG-93     21:09    NOAA-11     25.309
                                                   23-MAY-93     21:10    NOAA-11    24,024                  23-AUG-93     14:02    NOAA-12     11,8M
                                                   24-MAY-93     09.33    NOAA-11    24,031                  24-AUG-93     01:22    NOAA-12     11,930
                                                   29-MAY-93     10:14    NOAA-11    24,102                  24-AUG-93     13:41    NOAA-12     11,837
                                                   294AAY-93     21:38    NOAA-11    24,109
                                                   30-bAAY-93    10:M     NOAA-11    24,116                  11-SEP-93     10:41    NOAA-11     25,5g5
                                                   30-MAY-93     21:25    NOAA-11    24,123                  21-SEP-93     10:21    NoAA-11     25,726
                                                   31-MAY-93     09:50    NOAA-11    24.130                  22-SEP-93     00:57    NOAA-12     12,242
                                                   314UY-93      21:13    NOAA-11    24,137                  23-SEP-93     09:54    NOAA-11     25,754
                                                                                                             23-SEP-93     21:19    NOAA-1 1    25,761
                                                   01-JUN-93     21:01    NOAA-11    24,151                  U-SEP-93      09:43    NOAA-1 1    25,76S
                                                   01-BM-93      09:37    NOAA-11    24,144                  24-SEP-93     21:08    NOAA-11     25,775
                                                   02-JUN-93     09:23    NOAA-11    24,158                  28-SEP-93     22:00    NOAA-11     25,932
                                                   04-JUN-93     10:41    NOAA-11    24,197                  29-SEP-93     10.24    NOAA-11     25,&39
                                                   05-JUN-93     10:29    NOAA-11    249201                  29-SEP-93     21:47    NOAA-1 I    25vg46
                                                   05-JUN-93     21:55    NOAA-11    24,208                  30-SEP-93     10:11    NOAA-I 1    25,853
                                                   06-JUN-93     10:17    NOAA-11    24,215                  30-SEP-93     21:34    NOAA-11     2S,860
                                                   06-JUN-93     21:41    NOAA-11    24,=
                                                   07-YUN-93     21:28    NOAA-11    24,236                  01-Wr-93      09:59    NOAA-11     25,967
                                                   08-JUN-93     09:53    NOAA-11    24,243                  044)CT-93     11-02    NOAA-11     2s,910
                                                   09-JUN-93     09:39    NOAA-11    24,257                  044Cr-93      13:59    NOAA-12     12,420
                                                   10-JUN-93     09:33    NOAA-11    24,271                  05-OCr-93     01:19    MOAA-12     12,427
                                                   15-JUN-93     21:31    NOAA-11    24,349                  05-OCr-93     10:50    NOAA-11     25,924
                                                   16-JUN-93     09:56    NOAA-11    24,356                  06-OCr-93     22.02    NOAA-11     25,945
                                                   23-JUN-93     21:34    NOAA-11    24,462
                                                   24-JUN-93     21:22    NOAA-11    24v476
                                                   25-JUN-93     09:47    NOAA-11    24,493
                                                   25-JUN-93     21:10    NOAA-11    U,490
                                                   29-JUN-93     01:25    NOAA-12    11,034

                                Table 4.1a. Date and time (GMT) of acquisition, satellite and orbit numbers
                                                   of the 106 AVHRR images acquired through October 1986.

                                                                                                                                                                                                                                  136

                                                                                                                                                                                          Estimated
                                                                                                                     Method                                                    Depth          no. of
                                                                                                                    of data               Data        Measurement              range      map layers        GIS data
                                                                          Map layer(s)             Platform          capture              source          unit                  (m)       per survey          model

                                                                   Cetaccan surveys                ship           observers      GulfCet            numbers/species           0               1           vector or raster
                                                                                                   aircraft       observers      GulfCet            numbers/species           0               1           vector or raster

                                                                   Water temperature (WT)          ship           CTD/XBT        GulfCet              oC                       0-500           141         vector or raster
                                                                                                   ship           flow-thru      GulfCet              oC                       0               1           vector or raster
                                                                                                   satellite      AVHRR2         NOAA                   oC                       0               0-17+3      raster

                                                                   WT gradients4                   satellite      AVHR         NOAA                   oC/km                     0               0-17+       raster

                                                                   Water turbidity                 satellite      AVHRR          NOAA               plume/non-plume5          0               0-9+        raster

                                                                   Salinity                        ship           CTD            GulfCet            PSU                       0-500           14          vector or raster
                                                                                                   ship           flow-thru      GulfCet            PSU                       0               1           vector or raster

                                                                   Chlorophyll                     ship           CTD            GulfCet            Mg/1                      0               1           vector or raster
                                                                                                   ship           flow-thru      GulfCet            Mg/1                      0               1           vector or raster

                                                                   Sea floor maps                  ship           GLORIA'        USGS               0-255,                    -               I           raster

                                                                   Bathymetry                      ship           nolel          NMFS            m                        100-2,000       1           raster
                                                                                                   ship           note9           USGS/NOAA          m                         100-2,000       1           vector

                                                                   Coastline                                      nole10         DMA                longitude/latitude        -               I           vector

                                                                   Oil field structures                                          MMS                longitude/latitude                                    vector

                                                                   Survey transecu;                ship           LORAN-C        GulfCet            longitude/latitude                                    vector
                                                                                                   aircraft       LORAN-C        GulfCet            longitude/latitude                                    vector

                                                            1 Each map layer will correspond to a National Oceanographic Data Center (NODC) standard depth level, i.e., 0.                            10, 20, 30, 50, 75, 100,
                                                              12S, 150. 200, 250, 300, 400, or 500 m.

                                                             2 Advanced Very High Resolution Radiometer carried onboard the NOAA-11 and NOAA-12 polar orbiting Satellites.

                                                             3 Zero. partial. or full coverage of the GulfCet study area tip to twice each day per satellite depending upon the orbital path and Cloud cover.

                                                           4  Absolute magnitude of the sea surface temperature (SST) gradients derived from horizontal (cast-west) and vertical (north-south) SST
                                                              gradients extracted from each satellite-observed SST image using Sobel operators (Gonzales and Wintz 1977).

                                                           5  Mississippi River plume derived from the visible channels of the AVHRR using the algorithm described by Stumpf (1992) that aggregates
                                                              water into two classes: plume and non-plume.

                                                           6  Long-range side scan sonar referred to as the Geological Long-Range Inclined Asdic (GLORIA); the raw data were radiometrically and
                                                              geometrically  corrected and processed into sea floor maps by the U.S. Geological Survey (USGS).

                                                           7  no sea floor maps are 8-bit raster images with intensities ranging from 0 (no return) to 255 (strong return). The  intensities am directly
                                                              related to the backscattered sonar return which is a function of the sea floor gradient, bottom roughness, and sediment characteristics.

                                                           8  16-bt raster surface interpolated to a O.O1oX 0.01o longitude/latitude pixel size using National Ocean Survey point depth measurements
                                                              (1-min longitude/latitude spacing) and bilincar cubic spline functions; approximate area of coverage is 81-98o W longitude and 25-31o
                                                              N latitude.

                                                          9  Batju,etru lines manually digitized (in 10 m increments) from NOAA charts and included with the USGS GLORIA sea floor maps.

                                                          10 Gulf of Mexico coastline manually digitized from 1: 1.000.000 scale jet navigation charts and included as part of the Digital Chan ofth
                                                              World  a public domain dataset produced by the Defense Mapping Agency (DMA).

                                            Table 4.2. GIS data base characteristic for the map layers identified for the
                                                                        GulfCet project.

                                                                                                     137

                       absolute magnitude of the SST gradient image using 3 x 3 template masks
                      configured as Sobel operators (Gonzales and Wintz 1976) and an arithmetic
                      overlay operation (Aronoff, 1989 and Appendix, Volume 11). The visible
                      channels of the AVHRR from daytime overflights are also being processed into
                      turbidity images, primarily to examine the areal extent and location of edges of
                      the Mississippi River plume, using the algorithm described by Stumpf (1992).
                      A total of 199 AVHRR images have been acquired (as of October 6th) for the
                      study and are listed in Table 4.1. The satellite data products, shipboard and
                      aircraft observations of marine mammals, and environmental data collected
                      aboard the vessels will be included as map layers in the GIS data base (Table
                      4.2).

                      4.3.2.2 SHV12ort for the Whale Tagging -Effort

                      Satellite images acquired during September-October were selectively processed
                      into SST images and provided to colleagues at Oregon State University (OSU)
                      attempting to place satellite tracking tags on sperm whales in the Northern
                      Gulf of Mexico. A total of three SST images were processed during the two week
                      field effort and transferred to OSU using FTP/IP (INTERNET). A public domain
                      image processing package described by Leming (1989) that operates on a
                      minimally-equipped personal computer was also provided to enable the OSU
                      investigators to display the images in color and perform simple image
                      manipulation tasks.

                      Prior to the second tagging effort in June, OSU investigators were provided
                      with C-Coast software and set up to access satellite-derived SST and visible
                      channel images through the Coast Watch Gulf of Mexico Regional Node at SSC.
                      The PC-based C-coast software was developed with Coast Watch funding to
                      enable users to import, manipulate, enhance, and export Coast Watch image
                      products as well as overlay non-image data (e.g., sperm whale sightings).

                      4.3.2.3 GIS Procurement

                      The GIS hardware consists of a Silicon Graphics UNIX workstation and
                      peripherals; software is the Advanced Geographic Information System (AGIS),
                      developed by Delta Data sytem, and the Science and Technology Laboratory
                      Applications Software (ELAS), developed by the National Aeronautics and
                      Space Administration (Beverly and Penton 1989). A more detailed description
                      of the hardware and software is given in Volume II (Appendix).

                      4.3.2.4 AcQuisition of Collateral Data Sets

                      In addition to the satellite, survey, and environmental data being collected for
                      the project, other digital maps were tentatively identified for use in the GIS
                      data base and are listed in Table 4.2.

                      4.3.2.5 Infrastructural lmprovement5

                      There were a number of infrastructural improvements within the last year at
                      NMFS-SSC that will directly benefit the GulfCet effort, but completed at no cost
                      to the project. The FTP/IP (INTERNET) communications link became fully
                      operational and will be essential for the efficient transfer of data (particularly
                      digital maps) among investigators at NMFS, TAMUG, and OSU. The personal

                                                                                                   138

                     computers that will be used to support the project have been linked through a
                     local area network and have been upgraded from an MS-DOS operating
                     environment to an OS2/Windows environment. The CoastWatch Program
                     became fully operational in December 1992 and is available as a secondary
                     source of satellite observed SST images for the project. Major software
                     improvements were completed for the satellite receiving station last year to
                     streamline day-to-day operations of the unit. In addition to CoastWatch, the
                     station will serve as a backup source for satellite data.

                     4.3.3 GIS Data Management and Analysis

                     4.3.3.1 Base MaI2 Coordinate System

                     All of the digital map layers used in the GIS data base will be registered to a
                     portion of the Gulf of Mexico master image (GMMI) that includes the GulfCet
                     study area and thus encompasses the area from 26' to 31* N Latitude and 81' to
                     98* W Longitude. The GMMI is a raster image consisting of three land cover
                     classes: land, water, and land pixels adjacent to water (coastline). The file was
                     generated from vector coastline data reformatted from the Digital Chart of the
                     World data base (U.S. Defense Mapping Agency, 1992). The master image is
                     earth located with longitude/latitude coordinates using a simple cylindrical
                     projection (linear longitude/latitude) system (Snyder 1987). The dimensions of
                     each pixel in the GMMI are 0.01' longitude by 0.01' latitude. Longitude and
                     latitude coordinates are being collected concurrently with the cetacean survey
                     observations from aircraft and vessels and with shipboard measurements of
                     environmental variables using global positioning system or LORAN-C
                     receivers. These earth-located data will later be converted to AGIS map layers
                     and stored as either raster or vector files (Table 4.2).

                     4.3.3.2 Raster versus Vector Data Models

                     Some of the map layers tentatively identified for use in the GIS data base can
                     be stored as raster or vector data files (Table 4.2). The GIS software currently
                     available, with the exception of AGIS, will store and analyze raster or vector
                     maps, but will not handle both data types simultaneously. Thus, depending on
                     the software, mapping projects initiated with both types of data files require
                     conversion from one form to the other, i.e., raster to vector or vector to raster
                     prior to data basing and analysis. If a large number of layers have to be
                     converted for a particular project, the process can require a significant
                     amount of machine and staff time. Although the AGIS data base supporting
                     GulfCet could contain a mixture of both map types (Table 4.2), there are two
                     important operational concerns that have to be considered. First, the vector
                     model is a more compact data structure than the equivalent map stored in a
                     raster form (Aronoff 1989). Since most of the data volume in the GulfCet data
                     base will consist of raster maps (primarily satellite-observed data), there may
                     be slight advantage in storing other data layers (e.g., shipboard measurements
                     of salinity) as vector maps. However, online mass storage requirements for the
                     project were carefully considered when drafting the specifications for the
                     UNIX workstation. The 1.5 gigabytes of online storage (one hard drive and two
                     optical drives) descibed in Volume II (Appendix), should provide ample room to
                     store and analyze either a mixture of raster and vector maps or all of the data
                     as raster maps. The second and primary operational concern may be
                     processing speed; certain GIS analysis functions, e.g. overlay operations

                                                                                                     139

                      (Volume 11, Appendix,), are more efficiently implemented with raster maps
                      than with vector maps (Aronoff 1989). Some benchmarking will be conducted
                      to compare processing speeds of identical GIS tasks operating on (1) a mix of
                      raster and vector maps and (2) the same maps converted to raster files. Based
                      on the outcome of the evaluation, it may be more advantageous to convert all
                      of the maps to the raster domain given the anticipated volume of data that will
                      have to be processed for the project.

                      4.3.3 Processing Protocol

                      The GIS will be used for qualitative analysis of data structure by using such
                      functions as retrieval and classification and logical operations (Volume II,
                      Appendix) to create interactive map displays, tabular summaries, and data plots
                      in an effort to visualize relationships between the distribution and abundance
                      of cetaceans and satellite and shipboard measurements of environmental
                      variables. The dimensionality of the data, i.e., the potential number of input
                      variables for multivariate statistical analysis, is expected to be large since GIS
                      analysis tools such as proximity measures (Volume II, Appendix) will enable
                      analysts to explore the data in ways that would be virtually impossible using a
                      conventional analysis methods. The initial exploratory analysis will be
                      followed by a more formal, quantitative analysis of the data using multivariate
                      statistical techniques. Variables to be used in the analysis will be exported
                      from the GIS to one or more statistical software packages: (1) the Statistical
                      Analysis System (SAS) offering a wide range of univariate and multivariate
                      statistical procedures; (2) the Cornell Ecology Programs provide cluster,
                      detrended correspondence analysis, and ordination techniques for ecological
                      research (Gauch, 1982); and (3) SpaceStat spatial analysis software (Anselin,
                      1992).

                                                                                                  140

                     4.4 References for Section

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                     Aronoff, S. 1989. Geographic information systems: a management perspective.
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                     Biggs D.C. 1992. Nutrients, plankton, and productivity in a warm-core ring in
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                     Brooks, D.A. 1984. Current and hydrographic variability in the northwestern
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                     Behring, D.W. R.L. Moinary, and J.F Festa. 1977. The variability of anticyclonic
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                     Beverly, A. M., and P. G. Penton. 1989. ELAS - science and technology
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                     Fargion G. & R. Davis. 1993. GulfCet cruise 01 Hydrographic data. Technical
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