Simulating Effects of Nonintrogressive Hybridization with a Stocked Hatchery Strain of Rainbow Trout on the Sustainability and Recovery of Naturalized Steelhead Populations in Minnesota Waters of Lake Superior

Abstract A model was developed to explore the impacts of nonintrogressive hybridization with a stocked hatchery strain of rainbow trout Oncorhynchus mykiss (Kamloops strain [KAM]) on the sustainability and recovery of naturalized steelhead (anadromous rainbow trout) populations in Minnesota tributaries of Lake Superior. The model was used to assess the extinction risk of Lake Superior steelhead over a 50-year period based on multiple KAM stocking scenarios, initial population sizes, and levels of assortative mating. No extinctions occurred in simulated steelhead populations regardless of initial size after a one-time introduction of KAM; however, the risk of extinction due to nonintrogressive hybridization increased dramatically for scenarios involving annual stocking of KAM. The level of assortative mating among KAM and steelhead greatly influenced the risk of steelhead population decline or extinction for all scenarios. Results of the model support the contention that nonintrogressive hybridization coul...