Improving Return-to-Creel of Hatchery Catchable Rainbow Trout in Idaho through a Large-Scale Tagging Study

Idaho Department of Fish and Game (IDFG) hatcheries are integral to managing cold-water sport fishing opportunities in Idaho and continued efforts must be made to ensure that hatchery programs remain efficient while producing a quality product. Since 2011, IDFG has released over 140,000 T-bar anchor-tagged hatchery Rainbow Trout (Ocnorhynchus mykiss) as part of a multi-year, statewide evaluation of exploitation rates. In addition to monitoring angler catch across time and space, we evaluated returns-to-creel based on hatchery rearing density and length-at-release. All tagged fish were measured for length (mm) with the goal of releasing catchable trout that average 254 mm. While return-to-creel increased with decreased rearing density, returns were not high enough to offset the decreased production and length-at-release was the most significant factor influencing catch. Further evaluation indicated there was roughly a 7% increase in catch rates for each 25 mm increase in length-at-release. This has resulted in an increase in the average target size-at-release for a subset of catchables released annually. This size increase results in a roughly 40% decrease in production (quantity), but results in an overall increase in return to creel numbers, a higher percentage of the release being caught, and a better product for Idaho anglers.