Spawning and emergence phenology of bull trout Salvelinus confluentus under differing thermal regimes

Abstract

Median bull trout Salvelinus confluentus breeding was 2 weeks earlier in a cool stream than in a proximate warmer stream, aligning with expectations for salmonids, followed by emergence timing calculated to be 6 weeks later in the cool stream than the warm stream. This pattern is consistent with both site‐specific adaptation and thermal spawning threshold hypotheses for life‐history event timing in this threatened species.

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