Fish abundance upstream from Dworshak Dam following exclusion of steelhead trout. Technical completion report, project WRIP/371404

Fish abundance was determined by underwater fish counts in selected locations on twelve tributary streams of the North Fork Clearwater River, Idaho. Fish numbers, species composition and fish density were compared to results from previous studies of the watershed to determine what changes have occurred in the fish populations fifteen years after anadromous fish were excluded from the watershed by the construction of Dworshak Dam. Rainbow trout, Salmo gairdneri, continue to be the most abundant species in most tributaries of the North Fork Clearwater River. Average fish densities have decreased markedly since the elimination of the anadromous forms of rainbow trout (steelhead trout). Historically, large numbers of juvenile steelhead trout utilized the habitat in the tributaries of the North Fork of the Clearwater River, but resident forms of rainbow and cutthroat trout, Salmo clarki, are not fully utilizing this space. Further studies to increase the potential for fish production are suggested, including evaluation of introducing adfluvial or later-maturing stocks of rainbow and cutthroat trout