Effects of road-stream crossings on stream geomorphology and the movement of small bodied fishes in the Etowah River Basin, USA
Norman, James Randolph
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I evaluated the efficacy of the U.S. Fish and Wildlife Service’s Reasonable and Prudent Measures (RPMs) in protecting federally listed fish species by minimizing effects of road-stream crossings on channel geomorphology and fish movement. Measurements at 11 crossings constructed under RPM terms and conditions showed that RPMs were relatively effective in preventing changes to channel geomorphology with respect to channel depth and substrate composition, but less effective in preventing channel width changes and blocked fish passage. In a separate study, mark-recapture studies at four road crossings showed varying degrees of movement by small-bodied fishes (8 to 21 species per site) through culverts that differed in elevation above the streambed. Although none of the culverts were complete barriers to passage, only a bottomless-box culvert appeared to permit unrestricted, upstream and downstream movements by benthic and water-column fishes, based on multi-state model estimates of movement probabilities.