Microsatellite variation suggests substantial gene flow between king mackerel (Scomberomorus cavalla) in the western Atlantic Ocean and Gulf of Mexico

We developed microsatellite loci for king mackerel (Scomberomorus cavalla) and used them to investigate population structure and gene flow between samples from regional localities in the western Atlantic Ocean (Atlantic) and Gulf of Mexico (Gulf). Based on mark-recapture and spatial-temporal sampling, king mackerel in US waters have been perceived as organized into two or more "migratory units" that tend to move in the spring from southern wintering areas off south Florida and the Yucatan peninsula to more northern spawning areas along the southeastern US coast and the northern Gulf. We surveyed allelic variation at five microsatellite loci between samples of king mackerel from eight geographic localities in the Atlantic and Gulf. Tests of homogeneity in allele distribution indicated that two samples from the northern Gulf (Port Aransas, TX, and Gulfport, MS) differed significantly from the remaining samples. However, no significant genetic differences were found between samples representing geographic extremes, and no significant geographic patterns of genetic divergence were found when samples were combined into regional groupings reflecting current hypotheses of population structure. There also was no evidence of an isolation-by-distance effect. We hypothesize that the regional migratory groupings in king mackerel do not restrict gene flow to the extent that significant genetic population structure may arise. (C) 2002 Elsevier Science B.V. All rights reserved.