Diel patterns of foraging and microhabitat use by sympatric rainbow trout and bull trout: implications for adaptive differentiation and instream flow assessment

Salmonids make flexible and adaptive trade-offs between foraging efficiency predation risk that result in variable patterns of diel activity habitat use. However, the following remains unclear: (1) how differ among salmonid species; (2) this affects interpretation suitability models inform instream flow management. We combined snorkel observations with experimental additions cover to investigate risk, cover, bioenergetics affect use by sympatric rainbow trout (Oncorhynchus mykiss) bull (Salvelinus confluentus) Skagit River, British Columbia, Canada. Both species foraged primarily at dusk, supporting well-described trade-off risk. only responded additions, suggesting tolerance nature foraging-predation species. Diel shifts also substantially altered predictions models, potentially large consequences for