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 23°C. However, angler catch declined similarly as water temperature increased, from 5.2 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.

Bibliographic Information