Contribution of Hatchery-Reared Fish to Chinook Salmon Populations and Sport Fisheries in Lake Superior

Abstract

Chinook salmon Oncorhynchus tshawytscha stocked in Lake Superior since 1967 to diversify the sport fishery were suspected of reproducing. An abundance of naturalized chinook salmon would reduce the need for hatchery fish but also would decrease our ability to manage chinook populations and their effect on the Lake Superior fish community. Our study objective was to determine the relative contribution of hatchery and wild fish to chinook salmon populations in Lake Superior. All chinook salmon stocked in Lake Superior in 1988, 1989, and 1990 were marked with an agency-specific fin clip. Contribution of these marked year-classes were determined from their representation in sampled sport fisheries and spawning runs. Hatchery fish made up 9, 25, 32, and 57% of chinook salmon sampled in Ontario, Michigan, Wisconsin, and Minnesota waters of Lake Superior during 1990–1994. Hatchery chinook salmon stocked by each state or provincial agency were caught in each of the other Lake Superior jurisdictions, and two fish stocked by Michigan were captured in Lake Michigan tributaries. Chinook salmon stocked by Minnesota contributed most hatchery fish to sport fisheries in Michigan, Wisconsin, and Minnesota (10, 15, and 31%), and 1% in Ontario. Chinook salmon stocked by Michigan contributed 8% to Michigan sport fisheries and 5, 6, and 1% to Wisconsin, Minnesota, and Ontario sport fisheries, respectively. Wisconsin hatchery fish contributed 9% to Wisconsin sport fisheries and 5, 13, and 1% to Michigan, Minnesota, and Ontario sport fisheries. Fish stocked by Ontario contributed 5% to Ontario sport fisheries, and 2, 3, and 7% to Michigan, Wisconsin, and Minnesota sport fisheries. Chinook salmon spawning runs were reported in 10 Michigan, 8 Wisconsin, 4 Minnesota, and 19 Ontario tributaries during 1990–1994. In stocked tributaries, most chinook salmon in spawning runs were hatchery fish (70–89%), and in nonstocked tributaries most were wild fish (72–94%). Hatchery-reared chinook salmon were estimated to make up 25% or less of total chinook salmon populations in Lake Superior. Individual agencies must determine if this contribution is sufficient to justify continued stocking.