Influence of large woody debris and a bankfull flood on movement of adult resident coastal cutthroat trout (Oncorhynchus clarki) during fall and winter

To improve understanding of the significance of large woody debris to strea m fishes, we examined the influence of woody debris on fall and winter move ment by adult coastal cutthroat trout (Oncorhynchus clarki) using radiotele metry. Fish captured in stream pools containing large woody debris moved le ss than fish captured in pools lacking large woody debris or other cover. F ish from pools lacking cover commonly moved to habitats with large boulders or brush, particularly during the day. Movements by fish over 1-day period s were strongly influenced by large woody debris or other elements providin g cover. Fish initially found in habitats lacking large woody debris, large boulders, or brush cover moved the most extensively, while fish initially found in pools with large woody debris moved the least. Fish did not move e xtensively in response to a bankfull flood, although some moved to habitat downstream of large woody debris in tributaries or secondary channels. Habi tat downstream of woody debris in the main channel was not used during the flood, apparently because of extreme turbulence. Overall, these observation s provide additional evidence for the value of habitat complexity to some s tream fishes and support previous observations of minimal effects of floodi ng on adult fish.