Development of a Genetic Monitoring Program for Stock Enhancement of Mississippi Spotted Seatrout (\u3ci\u3eCynoscion nebulosus\u3c/i\u3e)

The spotted seatrout is a coastal sciaenid fish that is intensively exploited in the northcentral Gulf of Mexico. A stock enhancement research program was initiated in 2004 to develop methods to culture juveniles and release them in natural habitats to increase recruitment in the fishery. The goal of this study was to initiate a genetic monitoring program for stock enhancement activities. Assays for 15 microsatellite loci were optimized. Simulations indicated that this panel of molecular markers was sufficient to identify recaptured hatchery fish with high confidence assuming genetic data on broodfish spawned to produce released fish were available. Stock structure analysis revealed an isolation-by-distance pattern in the studied range (Apalachicola, FL to Grand Isle, LA) where reproductive isolation is a function of geographic distance between populations. Contemporaneous effective population size estimates were larger in Mississippi and Louisiana than in Florida suggesting that population density and/or dispersal may be greater in the western part of the sampled range. Further characterization of dispersal and local genetic adaptation are warranted to define management units for the program. Simulations under a variety of scenarios indicated that released fish could contribute up to 30% of the breeding population in the wild, provided the effective size of the hatchery population is equal to the actual number of broodfish currently spawned to produce released fish (50). Continued monitoring of effective population size and of the contribution of hatchery fish to the fishery are needed to evaluate the impacts of stock enhancement on genetic diversity and adapt procedures