Maps show spread of invasive species in waters

The Nature Conservancy has developed maps to detail the migration of invasive species over time into Eastern U.S. waterways. The maps "show population increase and spread since the appearance of each species in the Great Lakes basin and beyond," Evan Kreager reports for Great Lakes Echo, a service of the Center for Environmental Journalism at Michigan State University.

"Sea lamprey, the first of the six invasive species to appear in the area, initially showed up in Lake Erie in 1921," Kreager writes. Another map, right, shows the migration of Asian carp from the Gulf to the edge of the Great Lakes basin from 1975 to 2013. Other maps show the migration of zebra and quagga mussels, Eurasian ruffe, sea lamprey, round goby and black carp. (Read more) (Map: Asian carp in 2012. In 1977 the fish were only reported in a small area in Arkansas, where they escaped from catfish farms, which imported them to control vegetation. To see the interactive maps click here)