SUBSTRATE REQUIREMENTS OF SPAWNING CHINOOK SALMON (ONCORHYNCHUS TSHAWYTSCHA) ARE DEPENDENT ON LOCAL CHANNEL HYDRAULICS

Micro-scale (<0.1 channel widths) physical conditions within channels ultimately exert a strong control on habitat selection by fish species. Data are presented demonstrating that micro-habitat requirements of spawning Chinook salmon ( Oncorhynchus tshawytscha) are strongly inter-related; fish utilized coarser substrate if associated with faster flow velocities. This was not observed to be controlled through a hydraulic sorting mechanism but, rather, related to the physical processes of spawning. Failure to consider the 'elastic' nature of Chinook salmon spawning requirements resulting from links between the physical parameters may have implications for river management practices such as restoration or setting environmental flows. Copyright (C) 2009 John Wiley & Sons, Ltd.