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Historically, less than 2% of steelheadOncorhynchus mykissstocked in river mouths on Minnesota tributaries to Lake Superior returned as adults. To investigate the influence of stocking location on adult return rates, similar proportions of age-1 steelhead were stocked in the mouth and throughout upstream reaches of the Knife River. A subset of steelhead stocked upstream were implanted with coded wire tags (CWT), which resulted in 18% of all fish stocked, regardless of location, possessing a CWT. A fish trap near the mouth of the river was used to sample emigrating age-0 through age-3 juveniles and returning adults. Of the steelhead stocked upstream 45% survived to emigrate. Electrofishing surveys and trap results indicated no steelhead remained in the river past age 2. No evidence was found that larger age-1 stocked steelhead displaced smaller age-1 wild steelhead. Only 12% of returning adults possessed CWTs, 6% less than the percentage stocked with CWTs (18%). Adult return rates for those stocked in the river mouth were 1.0% compared with 0.5% for those stocked upstream. Overall, stocking in the river mouth contributed 69% of the returning adults. Given these results, Minnesota fishery managers should continue to look for alternate ways to increase steelhead return rates if greater adult numbers are desired. Received February 12, 2013; accepted July 3, 2013 [ABSTRACT FROM PUBLISHER]

A model was developed to explore the impacts of nonintrogressive hybridization with a stocked hatchery strain of rainbow troutOncorhynchus 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 [ABSTRACT FROM PUBLISHER]