Influence of Stream Flow on Hydrogen Sulfide Concentrations and Distributions of Two Trout Species in a Rocky Mountains Tailwater

Abstract

Abstract Geothermal springs in or adjacent to streams can contribute hydrogen sulfide (H2S) and affect distributions of fish. We assessed the effects of H2S, relative to discharge, on the locations and movements of cutthroat trout Oncorhynchus clarki and brown trout Salmo trutta in a regulated river in northwestern Wyoming. Concentrations of H2S as low as 0.13 mg/L prevented upstream passage and habitation by trout over a 4.2-km reach of the river. The location of the downstream terminus of the H2S plume was relatively stationary; it varied little when discharge was stable at moderate flows (13.7–14.8 m3/s) and moved within a 300-m reach when flows were declining from 20.9 to 5.7 m3/s. Changes in water temperature and riffle area appeared to be the major mechanisms controlling the concentration and downstream influence of H2S.