Nov 09, 2012 - scientificamerican.com

North American freshwater fishes are going extinct at rates that concern scientists

We may not miss the phantom shiner, the thicktail chub, the stumptooth minnow or the harelip sucker, but these freshwater fishes are among 39 species (3.2 percent of North America's freshwater fish population) and 18 subspecies that have vanished from the continent's waters over the past century. By 2050 the tally could reach as high as 86, an extinction rate that is about 877 times higher than normal and that has accelerated in the past 20 years, according to a study in the September issue of BioScience. When so many fish disappear in a short period, “you know something's up,” says study author Noel M. Burkhead of the U.S. Geological Survey.

Many of the extinct freshwater fishes lived in the Great Lakes region and most likely died off because settlements and cities built on the lakes contributed to pollution, overfishing and the introduction of nonnative species that outcompeted them. As compared with saltwater and terrestrial animals, freshwater species are particularly vulnerable because many depend on small, local water bodies. “The numbers should be a wake-up call that we urgently need to apply freshwater conservation efforts,” says Marguerite A. Xenopoulos of Trent University in Ontario, who authored a 2005 study on freshwater fish extinctions but was not involved in the current research.

Scientists are still working to understand what impact these extinctions might have on other populations. Although they understand the dynamics of large ecosystems, ecologists cannot yet “predict what the loss of a certain organism would mean,” Burkhead says. These fish are “doing something beneficial. We just don't know what all those benefits are yet.”

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