Summer habitat utilization and ecology of cutthroat trout fry (Salmo clarki) in Cascade Mountain streams

lectively called "lateral habitats," of three study streams with different riparian vegetation. Most fry remained inthese lateral habitats until the end of their first summer. The abundance of cutthroat fry was proportional to thearea of lateral habitat in each of the study streams. Average size and growth rate of fry were related to the effectof site elevation on stream temperature and the influence of riparian vegetation on the availability of invertebratefood. Lateral habitats are characterized by slow, shallow-water, abundant detritus and benthic invertebrate assem-blages of high density. Stream margins and backwaters provide gradients of depth and velocity, cover, and accessto food that are appropriate to the habitat requirements of fry. Because fry populations are closely related to theabundance and quality of lateral habitats in small streams, these habitats should be included in the assessmentof habitat requirements of cutthroat trout.