Genetic analysis of white marlin (Tetrapturus albidus) stock structure

The genetic basis of stock structure of white marlin (Tetrapturus albidus Poey, 1860) was inferred from analyses of five tetranucleotide repeat microsatellite loci (n = 214) and the mitochondrial (mt)DNA control region (n = 99) of white marlin from four geographic regions in the Atlantic Ocean. Considerable genetic variation was present in all collections for all molecular markers. Analysis of replicate collections taken in different years from three regions revealed no significant differences in the distribution of allele frequencies among years within regions. The value of global F-statistics for both multilocus microsatellite data and mtDNA control region sequences approached significance (0.0022, P = 0.057, and 0.0163, P = 0.069, respectively). Pairwise comparisons of regional collections based on microsatellite data revealed one significant comparison (western North Atlantic vs western South Atlantic), as did pairwise comparisons of mtDNA control region values (western North Atlantic vs Caribbean), and inferences from analysis of molecular variance (AMOVA) differed between mitochondrial and nuclear markers. However, there was a general trend for increased genetic divergence with increased geographic separation for both sets of markers. While these results are consistent with current management of white marlin as a single stock, the observation of significant heterogeneity warrants further analysis.