Distribution and abundance of marine mammals in the north-central and western Gulf of Mexico interim report

[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

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.

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

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

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

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

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.

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).

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.

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

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.

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.

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.

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.

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.

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.

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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).

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

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.

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:

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

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.

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).

0
CNI 0

+ 4+

-4f +

+ +.

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.

0 0
0 0
0 LD 0
C:) CIJ0

:+
+ +

+ +

+ 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.

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.

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.

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.

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).

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,

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

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

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.

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

(IQ

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9 8 00
31 2 9

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CD N 0

Co
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@+ ++ +#+

C:) CM
(M CM
00 CD Co Co
CD N

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

(JQ

CA W
@FO@Q*
zr 0
9 0 00
(IQp
CA " 31 0 0

CrQn

W +
2 5 2 9
0
CD

Iz
(D

Un
Co N CM

00 Co

C3
a

Co
Co Co C\I 03
CT) . . M

rn C\j

Figure 3.10. On-effort daylight cruise track and location (+) ofcetacean
sightings during Leg 2 of winter surveysummer survey, NOAA
ship.

0 coo
@r )-.
QQ o
-r
" 0
98: 00
OQ 31 0 a

(IQ

CJQ

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

CD
"
rA

2 5 2 9
98 00

7
(-D
z
0
RD

SPECIES SUMNER-SPRING WINTER

Balaenoptera edeni 1
Balaenoptera edenilborealis 3
Physeter macrocephalus 19 9
Kogia breviceps
5 1
Kogia simus
18 -
M 0 Kogia sp.
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

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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tD CD W W
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+
+44,

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m CD

C3
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M
C\j

C3 C:)
M C\j

+++$

+ #+ *+
+0 4
*# 00 + +
+4
+ +

CM M CO
M CIO M

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

98 00
3 1 :2 9

(D
t3
0

CIQ

0
QQ

2 4 0 0
I@DcrQ 98: 00
cn

C@ C3
C\j C
C3 C3
C\j0

*+
14

+ ++

0 0
C3 0
M M M
M Cv CD a]

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

(IQ

98: 00
31 2 9
0

C-D
ca

CD tn
0 (b
0 r.
cn
:31 (IQ
CD 'I
0
0
10

IQ
0

2 4 0 0
CD Ca,
go 00

QQ
C*l

+ +

CO Cn M w
CD a]

M Cv

Figure 3.17. Locations of Physeter macrocephalus groups sighted
during SEFC marine mammal cruises in the northern Gulf of
Mwdco: 1990- 1992.

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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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.

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

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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

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Cruise species Total
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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

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.

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.

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.

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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6/23/93 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
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0
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Date Time(CDT) Lat/Long What Number

10 6/7/93 1420 28040. 64/89005. 69 Tursiops truncatus 2
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: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

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.

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.

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.

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.

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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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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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4.2.4 Shipboard Measurements and Procedures

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

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-

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

All TS Data: GulfCat Cruises 2-6
35
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................... .... . .... ...........
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Figure 4.6. T-S Plot: all C`TD data Cruises 2-6.

30.000 CP

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Gulfcet Cruise 04 - All Stations

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

30.000

ct2o.000 . ...... ...... ...... ..... ...... ...... ..... ...... ...... ... ............ .
0
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Spring Cruises (01 and 05)

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

Summer Cruises (02 & 06)
35
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30 ..........

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

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

30.000

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

c
101,

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.

All Data from T-I 0 XBTs
0

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.

All T-7 XBTS
0

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

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

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.

All Data from T-20 XBTs
0

200

400

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.

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.@

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

Qn
0
28.5

CD Iva
0 1-1

aft
aft
27.5 no

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

0
0 28.5
C)

27.5

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

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

"0.0

(D
27.5 -
240.0 %
280.0

-0
(D
'P.0

26.5

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

(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

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

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

LSU Earth Scan Lab

Coastal Studies Institute

NOAA-11 SST

12 FEB 1993 100OZ

iii:- S,
Rx. W, A

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

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

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

26.5

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

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

00
0 28.5
C)

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

: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

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

29.5

0
@o
0 28.5
(JQ

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

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

26.5
CA

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
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

0
10
0 28.5

26.5
CD
W

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

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

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

Uj
CA

CD
CV

28.5

rA
rD 0.0
CIL0.0

26.5

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

: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

0
0
28.5

uj
EI
CL

26.5

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

(D 26.5

CrQ
0

25.5

(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)

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

35-5
QQ

(D 26.5

QQ
r_
co)

I.-
%Z

24.5
-96.5 -94.5 -92.5 -90.5 -88.5

131

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

Anselin, L. 1992. SpaceStat tutorial - a workbook for using SpaceStat in the
analysis of spatial data. Technical Software Series S-92-1, NCGIA, Department
of Geography, University of California at Santa Barbara, Santa Barbara,
California.

Aronoff, S. 1989. Geographic information systems: a management perspective.
WDL Publications, Ottawa, Canada, 294 pp.

Biggs D.C. 1992. Nutrients, plankton, and productivity in a warm-core ring in
the western Gulf of Mexico. J.Geophys.Res., 97:2143-2154.

Biggs D.C. M.M. Crawford, D. Salas et al. 1990. A US-Mexico cooperative study of
a cold-core ring in the western Gulf of Mexico. In Proceedings, 11th Annual
Gulf of Mexico Inf. transfer Mtg., 13-15 November, New Orleans, 374-380.

Brooks, D.A. 1984. Current and hydrographic variability in the northwestern
Gulf of Mexico. J.Geophys.Res. 89: 8022-8032.

Broks, D.A. and R.V. Legeckis. 1982. A ship and satellite view of hydrographic
features in the western Gulf of Mexico. J.Geophys.Res. 87: 4195-4206.

Behring, D.W. R.L. Moinary, and J.F Festa. 1977. The variability of anticyclonic
current pattern in the Gulf of Mexico. J.Geophys. Res. 82 (34): 5469-5476.

Beverly, A. M., and P. G. Penton. 1989. ELAS - science and technology
laboratory applications software. Volume II, user reference. Report 183,
Science and Technology Laboratory, National Aeronautics and Space
Administration, Stennis Space Center, Mississippi.

Fargion G. & R. Davis. 1993. GulfCet cruise 01 Hydrographic data. Technical
Report 92-01-T of the Department of Marine Biology Texas A&M University,
Galveston, 1-76 pp.

Fargion G. & R. Davis. 1993. GulfCet cruise 02 Hydrographic data. Technical
Report 92-02-T of the Department of Marine Biology Texas A&M University,
Galveston, 1-127 pp.

Fargion G. & R. Davis. 1993. GulfCet cruise 03 Hydrographic data. Technical
Report 92-03-T of the Department of Marine Biology Texas A&M University,
Galveston, 1-141 pp.

Fargion G. & R. Davis. 1993. GulfCet cruise 04 Hydrographic data. Technical
Report 92-04-T of the Department of Marine Biology Texas A&M University,
Galveston, 1-151 pp.

Fofonoff N.P. and Jr. R.C Millard. 1983 Algorithms for computation of
fundamental properties od seawater. UNESCO Technical Papers in Marine
Science, No 44.

Gauch, H. G. 1982. Multivariate analysis in community ecology. Cambridge
University Press, Cambridge, Massachusetts, 298 pp.

141

Gonzales, R. C. and P. Wintz. 1976. Digital image processing. Addison-Westley
Publishing Co., Reading, Massachusetts, 431 pp.

Herring, H. J. 1993. A bathymetric and hydrographic climatological atlas for
the Gulf of Mexico. Draft Report No. 109 produced for the U.S. Department of
the Interior, Minerals Management Service, Technical Analysis Group,
Contract No. 14-12-0001-30631.

Hofmann E.E. and S.J. Worley. 1986. An investigation of the circulation of the
Gulf of Mexico. J. Geophys. Res., 91:14221-14236.

Ichiye, T. 1967. Circulation and water mass distribution in the Gulf of Mexico.
Geophis. Int. 2:47-76.

Leming, T. D. 1989. Satellite imagery analysis/PC data link for directed
butterfish fishing. Final report - phase 1. Contract no. 89-009-245,
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