Developing a genetic baseline for the yellowtail amberjack species complex, Seriola lalandi sensu lato, to assess and preserve variation in wild populations of these globally important aquaculture species

Recent study suggest the globally distributed yellowtail amberjack, Seriola lalandi sensu lato, is a complex of three closely related species. Together, these and three other species of Seriola comprise an important component of global aquaculture production with an estimated annual value of $1.3 billion. As yellowtail aquaculture grows, the impact of unintentional releases on wild populations has become an increasingly important issue, particularly in light of international trade of hatchery seed. To create a genetic baseline, we examined spatial genetic structure in 260 specimens collected from seven locations over a wide geographical range using 15 nuclear microsatellites and mitochondrial control region sequences. Overall genetic differentiation among locations, as revealed by microsatellite data, was highly significant (F-ST = 0.085, D-EST = 0.382, P < 0.001), and pairwise estimates of divergence derived from mitochondrial and microsatellite data support the presence of four significantly differentiated populations corresponding to the N.E. Pacific, N.W. Pacific, S. Pacific, and South Atlantic. Based on the genetic differentiation detected in this study, and recently published sequence data, these populations more accurately reflect the presence of at least three cryptic species of Seriola. Especially strong genetic differentiation between hemispheres indicates that the equatorial region is a significant dispersal barrier for yellowtail. This study represents the broadest geographic investigation of genetic population structure conducted, to date, for specimens of the S. lalandi complex.