Factors Affecting the Vulnerability of Juvenile Coho (Oncothynchus kisutch) and Chinook Salmon (O. tshawytscha) in a Saltwater Sport Fishery

Abstract

The fork length, origin (hatchery or wild), and sex and age composition of sport- and seine-caught juvenile (no sea winter annulus) coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) were compared in Saanich Inlet, British Columbia. Sport-caught coho and chinook were larger and had a higher proportion of males than seine-caught fish. The sport fishery was strongly size- selective for both species, resulting in the overrepresentation of jack coho and freshwater age 1 juvenile chinook in the sport catch. Marked coho and chinook were overrepresented in the sport catch, indicating that hatchery fish were more vulnerable to the sport fishery than wild fish. For both species, the higher vulnerability of hatchery fish to the sport fishery could not be fully explained on the basis of size, sex, or freshwater age. Relative to older fish, juvenile coho and chinook were more vulnerable to fishing methods that used light gear at shallow depths (<30 m), such as trolling and casting. Assumptions by managers that vulnerability of coho and chinook does not vary with size, sex, freshwater age, or origin need to be reexamined in light of these findings.