Prodding the 800 Pound Gorilla: Evaluating the Assumption That Exploitation Rates Derived from Hatchery Produced Fall Chinook Salmon Are Representative of Exploitation Rates of the Naturally Produced Stock from the Salmon River, Oregon

Many stocks of Pacific salmon originating in Oregon, Washington, British Columbia, and Alaska are harvested in both commercial and sport fisheries. That harvest is managed in part under the Pacific Salmon Treaty (PST). Since 1986 a domestic stock of Chinook Salmon has been coded wire tagged and adipose fin clipped (Ad+CWT) to serve as the PST exploitation rate indicator (ERI) stock for Chinook stocks originating from the north Oregon Coast.  However, likely differences between hatchery and wild salmon in terms of maturation rates, survival rates, and migration patterns call into question the reliability of using a domestic stock to represent wild fish.  We are conducting a paired release study in which wild fish are Ad+CWT and released, and the hatchery stock is also Ad+CWT and released per normal hatchery operation. We have successfully completed three years of wild juvenile tagging. We have begun to see recoveries of wild adults tagged as juveniles in past years (brood years 2011 and 2012). We intend for this study to help answer some of these questions regarding differential survival, maturation, and vulnerability to harvest and provide a framework with which to adjust existing analyses of harvest rates or to propose further evaluation.