Cooperative Fish and Wildlife Research Units Program: Wisconsin Fishery
Education, Research and Technical Assistance for Managing Our Natural Resources

Introduced salmonids (i.e., chinook and Coho salmon, rainbow and brown trout) support important recreational fisheries within the Lake Michigan ecosystem. These fisheries are primarily supported by stocking. However, some natural reproduction is known to occur within some tributary systems. Specifically, anadromous rainbow trout (i.e., steelhead) stocked into Lake Michigan are known to exhibit an adfluvial life history, migrating up tributaries for spawning. Wild offspring have been encountered in some of these tributaries, but it is not known whether these fish successfully outmigrate from these streams into larger tributaries or Lake Michigan. The primary objectives of our research are to determine if: 1) abundance of wild age-0 salmonids (primarily steelhead) varies among selected streams in relation to available habitat; 2) wild age-0 salmonids successfully outmigrate from Wisconsin tributaries into Lake Michigan or into larger tributaries and 3) potential bottlenecks related to stream temperature or annual flow regimes prevent successful outmigration from some streams. We will also compare mark-recapture methods used to estimate wild age-0 salmonid abundance to determine if a single sampling event following stocking of marked fish yields similar estimates to estimates derived from multiple sampling events.