Variability of Certain Life-History Parameters of Early Juvenile Gag Grouper (Mycteroperca Microlepis, Pisces

Gag grouper, Mycteroperca microlepis, compose an important recreational and commercial fishery along the Gulf coast and Eastern Seaboard of the United States (Coleman et al. 2000, Morris et al. 2000, and Musick et al. 2000). Like many Serranids, gag have a complex life cycle in which juveniles spend each summer developing within inshore structured habitats before joining the adult population offshore (Heemstra and Randall 1993, Koenig et al. 1996, Grover et al. 1998). As is the case with most fisheries, heavy fishing pressures have led to a decline in gag abundance (Renan et al. 1996). The most efficient policies to mitigate for these population have as of yet focused on adult gag preservation; this study, however, attempt to use select juvenile gag population metrics (abundance and date of fertilization) to provide crucial data that may one day assist in providing a juvenile-centric population model. Over the course of a three-year study, juveniles were captured in two regions; near the Florida State University Coastal and Marine Laboratory (Turkey Point Shoal and Lanark Reef sites) and inside of Saint Andrew Bay, Panama City. Otolith analysis was performed to determine age and fertilization date of the juveniles, and abundance statistics were determined for each year. It was found that, consistent with previous literature, average fertilization date varied significantly across years and sampling sites (range = 41.9 to 91.8). The 2009 field season exhibited a significantly earlier fertilization date for both regions, and only one specimen was captured in Saint Andrew Bay. The 2009 Turkey Point Shoal field season was the only occurrence where abundance significantly declined during the course of the field season. Various environmental and physical factors may have been responsible for the enormous interannual variation seen in both abundance and fertilization date, such as large-scale current patterns and predator densities in the two regions. While no concrete conclusions may be drawn from the data, this study was essential in expanding on background knowledge of early juvenile gag population dynamics.