Extinction of US fish species examined

North American freshwater fishes are going extinct at an alarming rate compared with other species, a U.S. government researcher says. Writing in the journal BioScience, Noel M. Burkhead of the U.S. Geological Survey reports the rate of extinctions increased noticeably after 1950, and although it has leveled off in the past decade the number of extinct species has grown by 25 percent since 1989. For his study he examined North American freshwater fish extinctions from the end of the 19th century to 2010, when there were 1,213 species in the continent. At least 57 North American species and subspecies have gone extinct since 1898, about 3.2 percent of the total species in the continent, Burkhead wrote. Extinctions in fishes are mostly caused by loss of habitat and the introduction of non-indigenous invasive species, researchers said. Despite the discovery of new species and the "rediscovery" of species once thought extinct, Burkhead predicts between 53 and 86 species of North American freshwater fishes will likely have gone extinct by 2050, and the rate of extinction is now at least 877 times the background extinction rate over geological time.