Genetic variation and spatial autocorrelation among young-of-the-year red snapper (Lutjanus campechanus) in the northern Gulf of Mexico

Saillant, E., Bradfield, S. C., and Gold, J. R. 2010. Genetic variation and spatial autocorrelation among young-of-the-year red snapper (Lutjanus campechanus) in the northern Gulf of Mexico. - ICES Journal of Marine Science, 67: 1240-1250. Temporal and spatial genetic variations at 18 nuclear-encoded microsatellites were assayed among age-0 Gulf red snapper (Lutjanus campechanus), sampled from the 2004 and 2005 cohorts in each of five regions in the northern Gulf of Mexico ( Gulf) and from a mixed-age group sampled off northwest Florida. Hierarchical analysis of molecular variance revealed genetic heterogeneity among habitat patches within regions, but not among regions. A significant, positive spatial autocorrelation of microsatellite genotypes among fish sampled within the geographic range 50-100 km was detected. Bayesian coalescent analysis of historical demography indicated a decline of nearly an order of magnitude in the effective population size for red snapper across the area surveyed. The highest posterior probability for the current effective population size was 2163, approximately four orders of magnitude smaller than the estimates of red snapper census size. The results of the study demonstrate that spatial genetic structuring among young-of-the-year red snapper in the Gulf occurs at small geographic scales and is consistent with a metapopulation stock-structure model of partially connected populations. This accentuates the importance of maintaining healthy local spawning populations of red snapper in all regions across the northern Gulf.