Freshwater mussels are one of the most endangered groups of animals in the United States. Yet they are an important part of river ecosystems, filtering water and providing habitat and breeding grounds for many species.

The California floater mussel is native to parts of the western United States but has disappeared from many locations. In Arizona, the species may be extirpated. Dams and other types of changes people have made to rivers have contributed to the mussels’ decline. Like other mussels, the California floater relies on host fish to disperse its larvae. Changes to rivers that impact fish movements or survival can thus lead to mussel declines.