Diel summer habitat use by bull trout, Salvelinus confluentus, in Eastern Cascades streams
Banish, Nolan Paul
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Diel habitat use by bull trout was assessed at the micro- and mesohabitat scale in Eastern Cascades streams during the summers of 2001 and 2002. Most bull trout observations occurred at night. Bull trout exhibited an affinity for the streambed, suggesting benthic behavior. Bull trout were found in deep, low velocity microhabitats with small substrata during the day and night. However, small bull trout were found shallower than were large and adult bull trout. Bull trout often were located in pool mesohabitats formed by large woody debris. Logistic regression models indicated bull trout distributions were influenced by microhabitat, mesohabitat, and stream-level variables. Bull trout distribution was positively related to stream depth, fine substratum, and pool mesohabitats, but negatively related to current velocity, rubble substratum, stream temperature, and the presence of brook trout. Successful management of bull trout might be best applied at a mesohabitat level to preserve summer rearing areas.