Origins of stocked and wild Chinook Salmon in sport fisheries suggest extensive interjurisdictional movement and natural reproduction in Lakes Michigan and Huron

ABSTRACT Objective Chinook Salmon Oncorhynchus tshawytscha have been stocked continuously in Lakes Michigan and Huron since the 1960s by state agencies and contribute to a multibillion-dollar sport fishery. We described the origin of Chinook Salmon landed by anglers at sites in Lakes Michigan and Huron during the nonspawning (April 1–August 15) and spawning (August 16–October 31) seasons to better inform fishery managers and stakeholders. Methods All hatchery Chinook Salmon of the 2011–2016 year-classes were coded-wire-tagged and adipose-fin-clipped to determine how fish from different stocking locations contribute to sport fisheries and to assess wild recruitment. Over 35,000 Chinook Salmon were recovered from open-water angling at 47 ports on Lakes Michigan and Huron during April through October of 2013–2019. Catch per effort of fish from 142 tag lots, each representing fish stocked in a specific region and year, were assessed alongside catch per effort of wild fish. Results Wild Chinook Salmon comprised the majority of sport-caught Chinook Salmon recovered for this study in both Lake Michigan (68.2%) and Lake Huron (71.3%) during the nonspawning season and were relatively consistent among recovery districts. Conversely, returning wild Chinook Salmon percent of catch varied among recovery districts during the spawning season and was highest in northeastern Lake Michigan, which suggests that this area was a focal point of wild production. In Lake Huron, wild Chinook Salmon percent of catch was low during the spawning season (26.1%), which suggests that wild production in that lake may primarily occur outside of the studied area. Catch of hatchery fish during the nonspawning season was largely independent of local stocking levels in Lake Michigan but not in Lake Huron. Catch in Lake Michigan was mostly comprised of fish from a wide range of stocking locations, including fish released in Lake Huron, but few fish stocked in Lake Michigan were recovered in Lake Huron. Chinook Salmon captured during the spawning season were more heavily comprised of fish stocked in the statistical district where they were caught than during the nonspawning season, consistent with homing to stocking locations. Conclusions These results demonstrate that Chinook Salmon spring–summer sport fisheries in Lakes Michigan and Huron do not depend on fish from local stocking events and are largely comprised of wild fish and fish stocked elsewhere. Chinook Salmon have a mixed population in Lakes Michigan and Huron during spring and summer and are only dependent on local stocking or wild production levels during the fall spawning season.