An Evaluation of Steelhead Yearling Stocking Locations on a Minnesota Tributary to Lake Superior

Hatchery reared steelhead yearlings were stocked both upstream and near the mouth of the Knife River, a major Minnesota tributary to Lake Superior, to determine if stocking location influenced adult return rates.   From 2003-2006 (2002-2005 year-classes) approximately 40,000 maxillary clipped yearlings were stocked annually in equal proportions both upstream and near the mouth of the Knife River.  Thirty-eight percent of all yearlings stocked in the upper reaches were implanted with a coded wire tag (CWT), which resulted in 18% of all stocked yearlings possessing a CWT.   A fish trap near the mouth of the Knife River was used to sample adult steelhead as they returned to spawn.  Of the 760 maxillary clipped adults sampled by the trap from 2005 – 2011, 12% possessed CWTs.  Overall, the percentage of adults that returned with CWTs was significantly lower than the percentage stocked with CWTs (p<0.001).  Return rates of yearlings stocked near the mouth were 0.6%, compared to 0.1% for those stocked upstream.  Based on these findings in addition to concerns that wild juvenile steelhead were potentially displaced in the upper reaches by larger stocked yearlings, we recommend that if steelhead yearlings are stocked, they be placed near the mouth.