IT’S SAID THAT BEFORE THE MADISON RIVER WAS DIVIDED INTO UPPER AND LOWER SECTIONS BY A DAM, IT WAS A PROLIFIC ARCTIC GRAYLING FISHERY. WEST OF THERE, STEELHEAD AND SALMON WERE ABUNDANT IN THE SNAKE AND COLUMBIA RIVER DRAINAGES OF THE NORTHWEST. THROUGHOUT THE EASTERN U.S., BROOK TROUT THRIVED. THE SAME IS TRUE FOR CATFISH IN CHINA, EELS IN GERMANY, CHUBS IN COLORADO, AND DOLPHINS IN PAKISTAN. BUT SINCE DAMS HAVE BECOME UBIQUITOUS WORLDWIDE, FISH HABITAT AND BIODIVERSITY HAVE FALLEN, WORLDWIDE.
Dams affect fish habitat, river flow rates, water temperatures, sediments, oxygen levels, timing of spikes and low water levels, and of course, fish passage.
“Fish passage,” which goes by other names like “fish migration,” “connectivity,” and in cases of restoration, “fish-barrier removal,” has been a hot topic among conservation-minded…