SEGREGATED HABITAT USE BY JUVENILE AND ADULT TROUT IN A FLOODPLAIN SPRINGBROOK
Mobile consumers, like fish, utilize a range of habitats throughout their life cycles, often to satisfy dietary and energetic needs at different life stages. We examined the population distribution and demographics of rainbow trout (Oncorhynchus mykiss) and rainbow-cutthroat hybrids (O. mykiss X clarkii bouvieri), by analyzing fish scales and generating size-at-age curves within two springbrook habitats on the Snake River floodplain, ID, USA: one experiencing periodic scour and one not scoured since 1997. We found that juvenile fish composed a greater proportion of trout occupying the scoured reach, while adults were more prevalent in the non-scoured reach. A complementary study of fish diets showed that juvenile trout were more reliant on a greater diversity of aquatic insects, whereas adult diets were dominated by fewer, and non-insect, prey. Taken together, the segregation in distribution and diets may reflect that the ability of trout to fulfill foraging needs may be linked to flow regime, as abundance and diversity of aquatic insects in these habitats are mediated by the frequency of scour.
James Paris (Co-Presenter/Co-Author), Stream Ecology Center, Dept. Biological Sciences, Idaho State University, firstname.lastname@example.org;
Colden Baxter (Co-Presenter/Co-Author), Idaho State University, email@example.com;
Rachel Brinkley (Primary Presenter/Author), Idaho State University, Brinrach@isu.edu;