The U.S. Fish and Wildlife Service is protecting two species of freshwater mussels, one of which is found in Arkansas.
Wildlife officials announced Monday that placing the sheepnose and spectaclecase species under the Endangered Species Act is part of a settlement agreement with the Center for Biological Diversity.
The spectaclecase is a seven-inch long mussel found in Arkansas and 10 other states. Officials say its population has declined by 60 percent.
The mussels are considered to be the most endangered group of organisms in North America. Wildlife officials say their health reflects the overall health of rivers because the mussels need clean water to survive.
Mussels eat by filtering small particles from the water and as a result make the water clearer.
Pollution, dams and mining are threatening them.