A small mussel that's found in the St. Croix River and few other places has been declared endangered by the federal government.
The snuffbox mussel has disappeared from 62 percent of the streams where it was historically found.
The survival of this native mussel — which can live for decades — is threatened by loss and degradation of habitat, due in part to pollution and sedimentation. Non-native zebra mussels are also a threat.
The National Park Service is raising snuffbox mussels and releasing them in the gorge area of Mississippi River Pool 2 in St. Paul, where water conditions have improved in recent years.