A comparison of population structure in black rockfish (Sebastes melanops) as determined with otolith microchemistry and microsatellite DNA

The black rockfish (Sebastes melanops) is a long-lived (<= 50 years) viviparous species with an extended pelagic larval period (3-5 months) and a broad continental distribution. Prolonged larval periods have been assumed to lead to widespread dispersal resulting in minimal population structure. We tested this assumption by comparing otolith microchemistry and microsatellite DNA of adult black rockfish from four locations in Oregon and Washington. We observed significant differences among locations in element-to-Ca ratios (Mg:Ca, Mn:Ca, Zn:Ca, Sr:Ca, and Ba:Ca) at the otolith edge, which represented the last year of life. Discriminant function analysis, based on otolith element-to-Ca ratios classified, on average, 64% of the fish to collection location, suggesting that the majority of individuals from these locations did not mix. Using microsatellite DNA, we observed significant genetic differences among adults collected 340-460 km apart (F-ST = 0.018 +/- 0.004). Using five and seven loci, 63% and 75% of the fish, respectively, were correctly assigned to collection location. These two techniques provided corroborative and complementary information on the population structure of S. melanops.