Effects of elevated water temperature on cutthroat trout angler catch rates and catch‐and‐release mortality in Idaho streams

Abstract

The concern is growing that angling may need to cease at elevated summer water temperatures to protect salmonid populations. Cutthroat Trout Oncorhynchus clarkii in streams were caught, marked and released using artificial dry flies at temperatures from 13.5 to 25.7°C to evaluate whether subsequent recapture with backpack electrofishing (an index of relative survival) was reduced when the water temperature was elevated at the time of landing, and to evaluate the effect of water temperature on angler catch rates. The electrofishing recapture rate of marked fish (i.e. relative survival) declined as water temperature increased, from 0.58 for fish landed at <21°C to 0.35 at 21–23°C and 0.17 at >23°C. However, angler catch declined similarly as water temperature increased, from 5.2 fish/h at <21°C to 4.1 fish/h at 21–23°C and 1.2 fish/h at >23°C. After accounting for both declines, fish mortality/angler might be higher at cooler water temperatures than at warmer temperatures. Therefore, inhibiting fishing at elevated water temperatures may not benefit trout populations any more than at cooler temperatures.

Encounter rates and catch‐and‐release mortality of steelhead in the Snake River basin

“…Meyer et al. (2023) found that angler catch of stream‐dwelling trout was reduced at higher temperatures. As such, Meyer et al.…”

“…As such, Meyer et al. (2023) noted that population‐level influences from catch‐and‐release angling may be higher at lower temperatures as a result of increased angler catch rates. Though some catch‐and‐release steelhead fisheries do exist at times when steelhead are exposed to water temperatures exceeding 19°C, few steelhead are present in Idaho during such fisheries, steelhead are likely seeking coolwater refuges, and fish may be less susceptible to being caught.…”

“…Additionally, steelhead experiencing water temperatures greater than 19°C were likely seeking coolwater refuges (e.g., Clearwater River). Meyer et al (2023) found that angler catch of stream-dwelling trout was reduced at higher temperatures. As such, Meyer et al (2023) noted that population-level influences from catch-and-release angling may be higher at lower temperatures as a result of increased angler catch rates.…”