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 could be an impediment to the sustainability and recovery of the steelhead population in Lake Superior.

Received June 14, 2010; accepted July 20, 2011

ACKNOWLEDGMENTS

We thank those who reviewed previous versions of this manuscript, including Charles Anderson, Mike McInerny, Loren Miller, Don Schreiner, and Dave Staples. In addition, we are grateful to Loren Miller for developing the initial model structure on which our model was based and to Dave Staples for his modeling advice.