MICROHABITAT PARTITIONING AMONG STREAM-DWELLING JUVENILE COHO SALMON, ONCORHYNCHUS-KISUTCH, AND DOLLY VARDEN, SALVELINUS-MALMA

In small (<2 m wide) streams on Prince of Wales Island, Alaska, coho 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. 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. -from Authors