Wild Steelhead Catch and Release Mortality and Encounter Rate Evaluation

Recovery of wild Snake River steelhead is contingent on a variety of factors. Protection and restoration of freshwater spawning and rearing habitat within Idaho is one key factor. Sport fisheries for hatchery steelhead and Chinook are important to Idaho’s anglers and it’s important that our salmon and steelhead fisheries and hatchery programs are consistent with the recovery of wild steelhead and salmon. Current methods for estimating wild steelhead encounter rates and catch-and-release mortality potentially contain multiple sources of error. This research was identified by the National Marine Fisheries Service as an alternative method to validate the encounter rates and catch-and-release mortality rates used to calculate the impact rate of wild steelhead in Idaho (NMFS 2019). To meet management objectives, understanding the influence, or lack thereof, recreational fisheries have on wild steelhead is crucial. Hence, the purpose of this research was to directly estimate angler-wild steelhead encounter rates, discern spatial and temporal patterns in angler-wild steelhead encounters, and estimate the subsequent mortality occurring from catch-and-release steelhead angling in Idaho. This research provides information for the management of recreational steelhead fisheries while enhancing conservation activities for wild steelhead.

The project was in coordination with the University of Idaho, which lead graduate study aspects of the proposal. A copy of resultant May 2022 Master’s Thesis, ‘Encounter Rates and Catch-and-Release Mortality of Steelhead in the Snake River Basin’ has been uploaded to the NOAA database.

Idaho’s steelhead fisheries limit impacts on wild steelhead stocks by requiring wild fish to be released alive. Nonetheless, catch-and-release (C&R) mortality associated with fishery encounters is well documented (Muoneke and Childress 1994). Currently, managers assume a 5% C&R mortality rate in steelhead fisheries based on work by Hooton (1987), but lower and higher rates have been documented (Klein 1965, Thomas 1995). C&R mortality is influenced by environmental factors and angler practices. Therefore, refining our understanding of C&R mortality within Idaho steelhead fisheries is vital to management of the fishery. It is also imperative to estimate encounter rates within the fishery. For instance, if only 1% of the wild population is subject to mortality, the overall impact rate remains low even if C&R mortality is high. This project provided improved understanding and informed impact rate estimation for Idaho’s steelhead fisheries. Improved understanding will also benefit habitat restoration and other conservation efforts by limiting fishery impacts on escapement into spawning tributaries.