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






            UTILIZATION OF NATURAL AND ARTIFICIAL


                               REEFS BY JUVENILE GAG
































                                   North Carolina Department of Environment,
            SH                           Health, and Natural Resources
            157.85
            A7                            Division of Marine Fisheries
            G74                           Morehead City, NC 28557
            1993



                                                 August 1993















                                  UTILIZATION OF NATURAL AND ARTIFICIAL
                                           REEFS BY JUVENILE GAG



      CIO                                             By


                                                Kurtis L. Gregg






            0                       Completion Report Project F-41, Study 2



       1.0  0-

             V'4



                                                 August 1993






                                   North Carolina Department of Environment,
                                         Health, and Natural Resources


                                          Division of Marine Fisheries
                                          Morehead City, NC 28557








                   This project was conducted under the Federal Aid in Sportfish Restoration
                   (Dingell-Johnson) Act through the Wallop-Breaux Amendment and funded, in
                   part, by the U.S. Department of the Interior, Fish and Wildlife Service, Project
                   Number F-41.
















                                     TABLE OF CONTENTS





          NEED   ..........................................................       1


          PRIOR KNOWLEDGE   ................................................      1


          OBJECTIVE  ......................................................       1


          APPROACH   .......................................................      1


          FINDINGS  .......................................................       3


          RECOMMENDATIONS     ..............................................      4


          LITERATURE CITED  ................................................      4


          ACKNOWLEDGEMENTS     .............................................      5











              STATE:        North Carolina                            PROJECT NUMBER: F-41


                                                                      SEGMENTS: 1-2



              STUDY TITLE:         UTILIZATION OF NATURALAND ARTIFICIAL REEFS BY JUVENILE GAG
                                   (STUDY 2)


              STUDY PERIOD: 1991-1992


              INVESTIGATOR: Kurtis Gregg


              NEED: High catch rates of juvenile gag (Mycteroperca microlepis) were observed on near-shore
                     patch and artificial reefs off North Carolina. Concerns regarding growth overfishing
                     and the role artificial reefs play in the early life cycle of gag prompted an investigation
                     of the migration patterns, factors influencing occupancy of reefs, and relative
                     abundance of gag on artificial and natural hard substrates.


              PRIOR KNOWLEDGE:            Gag are presently classified overfished by the South Atlantic
                     Marine Fishery Management Council (SAFMC 1991). Management of this species
                     includes a five fish daily bag limit and a minimum size of 20 inches TL (508 mm).
                     Anecdotal data indicated high catch rates of juvenile gag on near shore patch and
                     artificial reefs off North Carolina in the fall, however no quantitative data were
                     available to document these observations. Large numbers of juvenile gag have been
                     documented in inshore estuarine and high salinity (>20 ppt) riverine waters of the
                     Carolinasand areconsidered estuarine dependant (Keeneretal. 1988; Rossand Moser

                     1989).



              OBJECTIVE: To delineate the estuarine emigration patterns of juvenile gag and the factors
                     influencing occupancy of near shore patch and artificial reefs


              APPROACH: Young of the year (YOY) gag captured by commercial channel net fishermen
                     were tagged by Division of Marine Fisheries (DMF) staff in New River (Figure 1) in
                     1991 and 1992. Length frequency of YOY gag was documented from the tagging
                     data. Recaptures would document the directions and distances traveled by YOY gag.
                     One commercial fisherman maintained a log book to document the number of gag and
                     other groupers captured each night his net was set. This log book was analyzed to












                                           2





























                                New
                                Ri e





                                      x
                                      Christmas Rock
                                   +
                                   AR355














               Figure 1. Two study sites, AR355 and Christmas Rocki
                          off New River, North Carolina, 1991-1992.












                                                             3

                     document mean catch per unit effort for channel nets in New River, and to estimate
                     relative abundance of each species of grouper observed in these catches. Channel net
                     catch rates were analyzed to determine if relationships existed between high catch
                     rates and water temperature, salinity, lunar phase, and weather fronts.


                     Relative abundance of gag on an artificial and a natural reef were assessed by
                     conducting visual transects with SCUBA. The two study sites were 17 km from New
                     River Inlet at 18 to 22 rn depths (Figure 1). Three 20 m transects were marked at
                     each site. Sampling was conducted monthly from August through November 1991
                     and May through November 1992. Relative abundance of three size classes was
                     quantified. Young of the year, sublegal (< 20 in), and legal (> 20 in) gag were counted
                     on each transect by the lead diver of the buddy pair. Relative abundance of all gag and
                     each size class was compared between sites and between seasons on the same site.
                     Recruitment of YOY gag and geographical distribution of year classes was also

                     assessed from the transects.



              FINDINGS:     Tag returns showed YOY gag remained in estuarine waters through the fall,
                     however results were inconclusive due to lower than expected numbers of fish tagged
                     (N = 118 1) and a low recapture rate (2.6%). Distance traveled by recaptured fish
                     ranged from 0.5 to 32.0 krn with a mean of 3.4 ï¿½ 1.4 km. Most fish were
                     recaptured in the New River area however two were recaptured 32 km northeast at
                     Browns Inlet. Catch per unit effort was quantified for one channel net from 1 August
                     through 20 October 199 1. This net fished a total of 260.25 hours. Mean gag per net
                     hour was 3.81 ï¿½ 0.38. Mean grouper per net hour was 3.91 ï¿½ 0.38 including gag,
                     black grouper Wycteroperca bonaci) and red grouper (Epinephelus morid). Periods
                     with high catch rates were compared to water temperature, salinity, lunar phase, and
                     weather fronts. No correlation was found between high catch rates and these

                     environmental variables.



                     Relative abundance of gag was lower at AR355 (3.77/transect) than at Christmas
                     Rock (5.16/transect). YOY gag made up 5.9% of all gag at AR355 and 3.2% of gag
                     at Christmas Rock. Sublegal gag made up 52.9% of all gag at AR355 and 57.4% of












                                                             4

                     gag at Christmas Rock. Legal size gag represented 41.8% at AR355 and 39.4% of
                     all gag at Christmas Rock. The proportion of all gag represented by each size class
                     was similar at both habitats. Sublegal gag comprised the largest proportion (> 50%)
                     of the gag populations at the two sites.


                     The sampling period was divided into four seasons for analysis: spring (May, June),
                     summer (July, August), early fall (September) and late fall (October, November). Data
                     from both years were combined for seasonal analysis. Young-of-the Year (YOY) gag
                     were observed at AR355 only in late fall. YOY gag were observed at Christmas Rock
                     in early fall, and in late fall. Relative abundance of YOY gag was 83.5% higher at
                     AR355 than at Christmas Rock in late fall. Sublegal and legal size gag were observed
                     at AR355 and at Christmas Rock in spring, summer, early fall and late fall .


                     Recruitment of YOY gag to near shore patch and artificial reefs appears to occur in late
                     fall and early winter. Rate of recruitment was beyond the scope of this study due to
                     low numbers of tag returns. Sublegal gag were observed throughout the sampling
                     periods at the two sites which are 17 km from New River Inlet.


              RECOMMENDATIONS:             These results support the use of minimum size limits to manage
                     gag off North Carolina. Protecting sublegal gag on near shore patch and artificial reefs
                     should be possible because of the shallow depths of these reefs. Recommendations
                     have also been made to increase interstitial spaces in artificial reef construction to
                     provide habitat for juvenile gag on near shore artificial reefs.



              LITERATURE CITED

              Keener, P., G.P. Johnson, B.W. Stender, E.S. Brothers, and H.R. Beatty.
                     1988. Ingress of Post larval Gag, M-ycterpperca microlepis, through a South Carolina
                     Barrier Island Inlet. Bull. Mar. Sci. 42 (3): 376-396

              Ross, S.W., and M.L. Moser.
                     1989. Life History of Juvenile Gag, Mycteroperca microlepis, in North Carolina
                     Estuaries, Manuscript.












                                                            5

              South Atlantic Fishery Management Council     (SAFMC).
                     1991.    South Atlantic Fishery Management Council.          Amendment Number 4,
                     Regulatory Impact Review, Initial Regulatory Flexibility Analysis and Environmental
                     Assessment for the Fishery Management Plan for the Snapper Grouper Fishery of the
                     South Atlantic Region.




              ACKNOWLE13GEMENTS


                     Funding for this study was provided through the US Fish and Wildlife Service under the
              Federal Aid in Sportfish Restoration Program and from the North Carolina Division of Marine
              Fisheries. Thanks to the commercial fishermen for their cooperation. I also thank the DMF
              staff in the Wilmington and Morehead City offices for assistance with field sampling. My
              appreciation to D. Heatwole and B. Johnson for preparation of the manuscript.




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