ST. PAUL (AP) - A variety of native mussel species once wiped out by pollution are making a comeback on the Mississippi River between Minneapolis and St. Paul.

The mussels suffered when sewage, industrial waste and farm runoff began tainting the river. But biologists discovered about 15 years ago that the native species was starting to return thanks to efforts to improve water quality.

  Tamara Smith, an endangered species biologist with the U.S. Fish and Wildlife Service, likens mussels to a canary in a coal mine. She says mussels are a telltale sign of water quality.

Researchers say the mussels play an important role in the aquatic food web because they capture organic matter that's later consumed by fish and other animals.