Microhabitat Partitioning among Stream-Dwelling juvenile Coho Salmon, Oncorhynchus kisutch, and Dolly Varden, Salvelinus malma

Microhabitat use and partitioning among age 0+ and 1+ coho salmon, Oncorhynchus kisutch, and age 0+, 1+ and 2+ Dolly Varden, Salvelinus malma, was studied in small (<2 m wide), natural streams on Prince of Wales Island, Alaska, and in laboratory stream channels. Coho salmon occupied midwater positions that they defended from other fish. Dolly Varden were more closely associated with the stream bottom and were seldom territorial. For each species, the depth of water, depth of focal point, and distance to nearest fish increased with fish size, whereas the distance to nearest cover decreased as fish size increased. Most fish selected focal point velocities between 0.0–9.0 cm∙s−1.Woody debris was the most frequently used cover type and most fish occurred over gravel substrates ranging from 2–100 mm particle diameter. Habitat use by each species in the laboratory was similar to the pattern observed in the field. Each species occupied similar habitats both when alone and when the other species was present. Although habitat use by juveniles of coho salmon and Dolly Varden overlapped among several key parameters, each species primarily exploited resources not readily available to or selected by the other in the natural streams we studied.