Project title: Spawning potential ratio assessment and sensitivity analysis utilizing estimates of age at maturity and fecundity for Yelloweye Rockfish in Prince William Sound, AK
Personnel Donnie Arthur (MS Student) Funding source(s): Alaska Department of Fish and Game Project description: Yelloweye Rockfish (Sebastes ruberrimus) are a highly-valued catch in recreational and commercial fisheries throughout Alaska and make up an important portion of the subsistence harvest in communities along the Gulf of Alaska. However, no management or assessment strategies exist for Yelloweye Rockfish in Prince William Sound, and to date no abundance estimates have been made. In this study, we intend to create a framework or threshold for harvest that can be applied to the management of Yelloweye Rockfish in Prince William Sound. A Spawning Potential Ratio (SPR) model will be used to compare the spawning production per recruit at the current harvest level over its life time when compared to an unfished population. The model requires inputs such as the age (A50) or length (L50) at which 50% of the population is sexually mature. Our objectives are to, 1) generate estimates of A50/L50 through histological examination of Yelloweye Rockfish ovaries and generate a model for age-specific fecundity of the species in Prince William Sound, and 2) use the results from Objective 1 to build an SPR model for Prince William Sound Yelloweye Rockfish. Age or length at 50% maturity will be determined through histological (microscopic) examination of Yelloweye Rockfish ovaries. Due to a complex reproductive biology, not all female Yelloweye Rockfish can be determined to be sexually mature based on macroscopic observations. For example, rockfish are known to skip spawn (do not reproduce every year), and if assessment was strictly based on macroscopic observations, a skip-spawning mature fish would be falsely assigned an immature rating due to absence of eggs that given year. Work with the SPR model will be performed primarily using statistical/quantitative software such as Program R. The parameters entered into the model need to be accurate for a specific population. For example, age at 50% maturity is known to vary with latitude. In the southern range, Yelloweye Rockfish mature at 7 years of age and in Southeast AK, they mature at 22 years of age. Prince William Sound is the northern most distribution of this species, so we expect that the age at 50% maturity will be greater than the rest of the range. It is important to have accurate and representative estimates of these parameters because an overestimate of spawning production in the SPR model could result in a prescribed fishing level greater than the population can truly sustain.The recreational harvest of Yelloweye Rockfish in Prince William Sound has been increasing for over 15 years. This harvest coupled with commercial removals could result in harvest level that is already exceeding a sustainable level. The project is directed towards the conservation of this specific species in a particular region where it has economic and cultural importance. Co-Investigators: Anne Beaudreau (UAF) Trent Suttun (UAF) Brittany Blain (ADFG) Collaborators: University of Alaska Fairbanks, USGS, Alaska Department of Fish and Game |
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Presentations: Arthur, D, Falke, J., Blain-Roth, B, Beaudreau, A., and Sutton, T. 2020. Fecundity of Yelloweye Rockfish in Prince William Sound and the Northern Gulf of Alaska. 45th Annual Meeting for the Alaska Chapter of the American Fisheries Society, Fairbanks, Alaska, 23-26 March, 2020. Arthur, D., Falke, J., Beaudreau, A., Sutton, T., and Blain-Roth, B. 2019. Reproductive life history of Yelloweye Rockfish (Sebastes ruberrimus) in Prince William Sound and the northern Gulf of Alaska. 149th Annual Meeting of the American Fisheries Society, Reno, Nevada, 29 September -03 October, 2019. Arthur, D., Falke, J., Beaudreau, A., Sutton, T., and Blain-Roth, B. 2019. Reproductive life history and potential modeling for Yelloweye Rockfish (Sebastes ruberrimus) in Prince William Sound and the northern Gulf of Alaska. Alaska Chapter American Fisheries Society Annual Meeting, Sitka, Alaska, 19-22 March, 2019. |