Researchers at New York’s Queens College have found that fish ladders are not effective, according to the journal Conservation Letters. Fish ladders, which have long been an integral part of dams in the U.S., are meant to aid fish in reaching their natural spawning grounds.
Fish migrations were monitored through the Connecticut, Merrimack and Susquehanna rivers. The percentage of fish that made it through multiple ladders along the rivers were very low, less than 3 percent for American shad alone. Other species tracked include Atlantic salmon and river herring.
The researchers note that the results appear worse when the drop in overall fish migration is taken into account. Recent migrations pale in comparison to the massive migrations of the past, which numbered fish in the millions.
Image: A fish ladder on Hope Mills Lake in Hope Mills, N.C. (Credit: Brandon P, via Wikimedia Commons)