Summer Use of Simulated Undercut Banks by Juvenile Chinook Salmon in an Artificial Idaho Channel

Abstract

The effects of introducing simulated undercut stream banks on the distribution of juvenile chinook salmon (Oncorhynchus tshawytscha) were studied in a naturally vegetated, flow-regulated channel in Idaho in 1980 and 1981. In all tests, mean fish weight was greater in covered than in open sections. Preference for the covered versus uncovered experimental sections was highly significant during July and August tests. For all tests combined, 82% of the fish by numbers and 85% by biomass were collected in covered sections. The results suggest that undercut banks, as simulated by artificial shelters, are an important summer habitat component for juvenile chinook salmon that should be carefully evaluated by the manager.