Reproductive Biology of Pacific Ocean Perch Sebastes alutus in the Gulf of Alaska

Despite the ecological and economic importance of rockfish fisheries in Alaska waters little information is available concerning the reproductive biology of the majority of federally managed rockfish species in the Gulf of Alaska.  Many rockfish species or species assemblage assessments currently rely on age at maturity estimates that are drawn from small sample sizes or are based exclusively on macroscopic (visual) staging. This study re-examines the reproductive biology of Pacific ocean perch within the Gulf of Alaska utilizing histological techniques to microscopically examine ovarian tissue. Pacific ocean perch samples were obtained throughout the year during National Marine Fisheries Service and Alaska Department of Fish and Game scientific surveys, from the North Pacific Groundfish Observer program, and from scientific charters. Pacific ocean perch ovaries began to ripen during the months of August and September with yolk increasing until February.  Embryos appeared within the ovaries during February and March and continued to grow and develop until April and May when parturition occurred. Preliminary results indicate that length at 50% maturity is 33.3 cm FL and age at 50% maturity is 8.2 years. Both of these values are smaller than those currently utilized in the stock assessment of Gulf of Alaska Pacific ocean perch. Results from this study will improve the stock assessment of this species by providing more accurate reproductive parameter estimates and reducing the uncertainty in length and age at maturity estimates.