Grass carp, one of four Asian carp species threatening to invade the Great Lakes, including Lake Erie, may have done just that. Scientists with the U.S. Geological Survey this week announced that four adult grass carp taken from the Sandusky River had been born in the river, which means the species is breeding there. The river flows into Lake Erie at Sandusky Bay. Scientists fear that an invasion of grass carp, silver carp, black carp and/or bigmouth carp may wipe out the lake’s native plants and fish. See stories by NPR, the New York Times and USA Today. (Photo: Grass carp by Eric Engbretson, U.S. Fish and Wildlife Service, Bugwood.org.)