Location and Stock Identification of Spawning....
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GRANT NUMBER: NA57FD0030           NMFS NUMBER: 93-SER-023

REPORT TITLE:  Location and Stock Identification of Spawning Aggregations of Gag, Mycteroperca microlepis, along the Southeast Coast of the United States

AUTHOR:  South Carolina Department of Natural Resources

PUBLISH DATE:  August 29, 1996

AVAILABLE FROM: National Marine Fisheries Service, Southeast Region, 9721 Executive Center Drive, North Koger Building, St. Petersburg, FL 33702.  PHONE: (813) 570-5324


The goal of this project was to use rapid survey methods to locate gag (Mycteroperca microlepis) spawning aggregations and determine the relationship between spawning adults and juveniles recruited to nursery habitats. Using side-scan sonar to locate, and underwater TV (UWTV), and plankton sampling to confirm, spawning aggregations were located. The identity of stocks was determined by tagging and genetic work. DNA amplification techniques were used to identify individuals from specific spawning sites, and to determine if juveniles in estuarine nursery habitats can be identified as progeny form particular spawning aggregations.  Finally, the project determined sex ratios of gag in spawning aggregations throughout the South Atlantic Bight. The data indicated that gag are spawning north of Florida. Large adult gag in spawning condition were collected at the shelf edge off Charleston, South Carolina. UWTV noted the presence of few gag during the spawning season, but occasional groups were seen at the shelf edge. Plankton tows collected only one Mycteroperca spp. larva. Genetic analysis indicated no clear pattern of stock structure in gag, and suggested year class differences in microsatellite allele frequencies. To resolve this, a large sample size (at least 50 fish from each year class and from each area) and ageing data are needed.  Sex ratios of gag off the southeastern Atlantic coast have changed over the last 20 years, perhaps as a result of fishing pressure. 

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