Habitat Selection and Movement by Individual Cutthroat Trout in the Absence of Competitors

Abstract

If salmonids attempt to optimize their energy gain, then one could assume that all fish with knowledge of a particular environment would occupy the same habitat if it were not already occupied by a competitively dominant individual. We attempted to determine whether individual cutthroat trout introduced at separate times would select the same channel units within sections of stream when all larger trout were removed from those sections. Cutthroat trout disproportionately used pools, but not to the exclusion of riffles despite the absence of larger fish. In only one of seven sections did different cutthroat trout select the same channel unit throughout the study. In the remaining sections, they did not consistently occupy the same channel unit. We believe that incomplete knowledge of the available habitat, or little difference in food availability among a few habitats, may have caused the lack of consistent habitat selection.