Population structure of the gray snapper, Lutjanus griseus, in the U.S. waters of the Gulf of Mexico

Abstract

Gray snapper, Lutjanus griseus, comprise an important recreational fishery in U.S waters of the Gulf of Mexico (hereafter Gulf). Currently, gray snapper in the Gulf are managed as a single stock; however, there are no data on the population structure of the species. Population structure of gray snapper in the Gulf was assessed via homogeneity testing of allele and genotype distributions at 13 nuclear-encoded microsatellites and a 590 base-pair fragment of mitochondrial DNA. No significant differences in allele or haplotype distributions of either microsatellite or mitochondrial DNA were found in samples from five localities in the Gulf and one locality from the western Atlantic. These data are consistent with a single-stock hypothesis for gray snapper in the Gulf. Levels of genetic variation were comparatively low and analysis of demographic history revealed a two to three order-of-magnitude decrease in effective population size occurring over the past 5,000 years. The low genetic variation combined with the significant decrease in effective population size is compatible with the hypothesis that colonization of the Gulf by gray snapper occurred following the reduction in effective size, and that there has been insufficient time for genetic divergence to occur. Although there was no evidence of multiple stocks, the low levels of genetic variation and decline in effective population size may have implications for management of the gray snapper resource.