| Abstract: | Introduced brown trout, Salmo trutta , are common to many streams of western North America. However, the ecological interactions between brown trout and native stream fishes are not well understood, particularly the nature and extent of antipredator responses of native species. We examined the effects of brown trout presence on diurnal habitat use by 2 small native fishes at a mesohabitat scale (e.g., pool, riffle, run, backwater, etc.). Adult and juvenile southern leatherside chub ( Lepidomeda aliciae , formerly Gila copei ) and juvenile mountain sucker ( Catostomus platyrhynchus ) were located in main channel pools in the absence of brown trout, but they were found almost exclusively in backwaters and cutoff pools (i.e., off-channel habitats) in streams where brown trout were abundant. Off-channel habitat appears to provide a refuge for native fishes in streams with abundant brown trout populations. Altered or degraded streams may not include sufficient off-channel refuge habitats to allow coexistence of native species and introduced brown trout. |
