An Evaluation of Age-1 Steelhead Stocking Locations on a Minnesota Tributary to Lake Superior

Historically, less than 2% of steelhead Oncorhynchus mykiss stocked 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