An Evaluation of the Potential Cumulative Bioeconomic Impacts of Proposed Small-Scale Hydro Development on the Fisheries of the Swan River Drainage, Montana

Cumulative fisheries impacts of 20 small hydro projects proposed for tributary streams in the Swan River basin of northwestern Montana were investigated. Tributary fish populations consisted primarily of resident brook trout (Salvelinus fontinalis), resident westslope cutthroat trout (Salmo clarki lewisi), and juvenile bull trout (Salvelinus confluentus) from an adfluvial population residing in Swan Lake. The effects of total dewatering of project areas and increased stream sedimentation due to small hydro and forest development were predicted. Up to 4%, 18%, and 32% of drainage-wide populations of brook, cutthroat, and bull trout, respectively, could be lost if full development occurred, primarily because of dewatering. Individual stream populations could suffer losses as great as 50% for brook trout, 90% for cutthroat trout, and 84% for bull trout. Using creel and economic surveys, annual net values were estimated at $788,000 (travel-cost) for the entire Swan sport fishery and $232,000 (hedonic travel-cost) for the highly-valued migratory bull trout fishery. The estimated value to anglers of a 25% fish loss in the drainage varied from $250,000 (willingness-to-drive) to $2,600,000 (willingness-to-sell)