Genetic Mixture Analysis Supports Recalibration of the Fishery Regulation Assessment Model

Management of the commercially important Washington coastal Chinook Salmon Oncorhynchus tshawytscha troll fishery depends on the Chinook Salmon Fishery Regulation Assessment Model (FRAM). The Chinook Salmon FRAM uses historical and contemporary coded wire tag recoveries to estimate abundance and exploitation rates for particular indicator stocks. Those estimates are used to set limits on overall harvest and protect sensitive stocks. Current efforts are underway to implement a newer base period (time period on which exploitation rates are based). Our collaboration of science, management, and industry used genetic mixture modeling to provide independent stock composition estimates supporting FRAM recalibration. Genetic modeling suggested that total catch includes a much smaller proportion of a limiting Columbia River stock, a larger fraction of Canadian stocks, and an abundant Oregon coastal stock not previously included in the FRAM. Our results focus attention on particular stocks that will benefit from refinements in the Chinook Salmon FRAM.