Evidence of differential detectability of lotic adult rainbow and brown trout: Implications for habitat use inference from direct-underwater observation

Abstract

The number of observations of brown trout Salmo trutta was significantly lower than expected based on the ratio of estimated densities of brown trout and rainbow trout Oncorhynchus mykiss and the number of tagged rainbow trout and brown trout in a Sierra Nevada river. We believe that behavioral differences as well as abundant cover composed of large substrate in the study area were major factors contributing to the lack of brown trout observations relative to observations of rainbow trout. These results should be considered by managers and researchers who collect habitat use data for brown trout with direct-underwater observation because that data could be considerably biased. © 1997, Copyright Taylor & Francis Group, LLC.