Nestled in the gravel beneath the waves of many rivers there live small endangered species that at first glance appear to be no more than oddly shaped rocks. Silent and unassuming, many freshwater mussels are fighting their way back from the brink of extinction with help from the U.S. Fish and Wildlife Service.
Service staff from the Genoa National Fish Hatchery in Genoa, Wisconsin and the Twin Cities Ecological Services Field Office in Bloomington, Minnesota, are working with state and federal partners to restore the winged mapleleaf mussel to the Mississippi River and its tributaries. The winged mapleleaf was once prominent in the many waterways that lead into the Mississippi River. Today, the mussel’s existence is threatened by pollution and invasive species.
Complicating the recovery of the species is its unique approach to reproduction. Like most freshwater mussels, the successful reproduction of the winged mapleleaf depends on a host fish. Fertilized winged mapleleaf larva must successfully attach to the gills of a host fish, normally a channel catfish, to grow. Eventually the larva will fall off the host fish into the river bottom, where it will continue its journey to adulthood if the habitat is suitable where it falls.
Unlike a bear or eagle, a winged mapleleaf can fit in the palm of your hand. So how do Service staff find these small creatures year after year? Luckily, mussels tend to stay in one place. Divers place mussels along a fixed underwater line at a recorded location. Before mussels are placed along the line, they are marked with an identifying tag. By placing mussels together on a collection of lines located in the St. Croix River, divers can quickly locate winged mapleleaf mussels during their short breeding period.
Throughout late summer and early fall, Service employees check the lines to see if the mussels are reproducing, referred to as brooding. Winged mapleleaf mussels that are brooding are collected and transported to Genoa National Fish Hatchery where their larva are exposed to host channel catfish. The host catfish are kept at the hatchery until the spring, when they are then placed into cages in the wild for the young mussels to detach from their gills.
Reintroduction of the winged mapleleaf to the Mississippi and other rivers will take time, but with the help of the U.S. Fish and Wildlife Service and partners, the little mussel now has a fighting chance.