?A native freshwater mussel species of fast-flowing riffles in medium-sized rivers, the winged mapleleaf leads a complex life for an animal sometimes confused for a rock. Like many other freshwater mussels, this endangered species gets its name from its shape, and how it varies from its far more commonly found sister taxon the mapleleaf, a wing or protrusion along one side. Winged mapleleaf were once found in 38 places in the midwest from Minnesota to Arkansas, but are now found only in six.

The winged mapleleaf, like other species of mussels, spends most of its time buried in sediments and are primarily sedentary. To move, they use a hatchet-shaped muscle called a foot which contracts and allows the mussel to pull itself along. The St. Croix River in Minnesota contains the only populations known to be reproducing.

The winged mapleleaf is currently listed as an endangered species. Two of the main threats to the winged mapleleaf are habitat fragmentation and small population size. For example, the five remaining populations are largely or entirely isolated from one another and appear to be highly differentiated genetically, as noted by A.H. Hemmingsen in 2008. Thus, each may possess important local adaptations. Propagation of winged mapleleaf, and its reintroduction into historically occupied river reaches, could reduce the impact to the species’ genetic diversity that might result from the loss of any of the remaining populations. In addition, it may be an important tool to increase the viability of one or more populations. Along with several partner agencies, we are working to establish a successful protocol for producing winged mapleleaf in large enough numbers to effectively reintroduce the species.

Zebra mussels also (Dreissena polymorpha) impact the remaining populations of winged mapleleaf. Zebra mussels are an invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

Learn more about invasive species of mussel that threaten native freshwater mussels in the Mississippi River Watershed. They were inadvertently introduced into North America during the late 1980s and became established in the lower St. Croix River in 2000. Zebra mussels attach to any hard surface and breed so prolifically that they smother or otherwise harm native mussels. It is essential to the conservation of winged mapleleaf that zebra mussels are not allowed to invade any of the remaining winged mapleleaf habitat.

The St. Croix River population is near the major metropolitan area of Minneapolis and St. Paul in Minnesota. Therefore, major land use changes like urban development of the St. Croix River Watershed could result in increasing levels of contaminants and sediments in runoff that drains into the river. In 2008, D.J. Hornbach and M.C. Hove documented an increase in fine sediments in the winged mapleleaf habitat in the river. In Arkansas, Missouri and Oklahoma, agriculture and industry are abundant in the watersheds where winged mapleleaf are present. These activities can destabilize river corridors and increase runoff of harmful pesticides, chemicals and sediment.

On July 22, 1991, the species was added to the U.S. List of Endangered and Threatened Wildlife and Plants. This status makes it illegal to harm, harass, collect or kill the mussel. Scientific studies of winged mapleleaf or forms of take that is incidental to an otherwise legal activity may be allowed by obtaining a permit from the U.S. Fish and Wildlife Service. In addition to listing the species, U.S. Fish and Wildlife Service researchers developed a recovery plan to identify and prioritize actions necessary to recover this species.

Lastly, we have been working with Xcel Energy, which operates a dam upstream of the winged mapleleaf habitat in the St. Croix River to protect needed habitat. The energy company agreed with Wisconsin Department of Natural Resources to manage flows from its St. Croix Falls dam in a run-of-river mode. This effectively ended peaking operations at this facility that adversely impacted the important mussel beds just downstream. In addition, the National Park Service, the states of Minnesota and Wisconsin, the U.S. Army Corps of Engineers and others are cooperating with us to collectively keep zebra mussels out of habitat which is occupied by winged mapleleaf in the St. Croix River.