U.S. Fish & Wildlife Service

Higgins’ Eye Pearlymussel higginsii

The Higgins eye pearlymussel is an . Endangered species are and plants that are in danger of becoming extinct. Threatened species are animals and plants that are likely to become endangered in the foreseeable future. Identifying, protecting, and restoring endangered and threatened species is the primary objective of the U.S. Fish and Wildlife Service’s endangered species program.

What is the Higgins Eye Pearlymussel?

Appearance: The Higgins eye is a freshwater mussel with a rounded to slightly elongate smooth-textured shell that is usually yellowish brown with green rays. The shell, made up of 2 hinged, inflated halves, is up to 4 Photo by USFWS inches long with a rounded side and a pointed (males) or squared (females) 50% of the historic range, which Reproduction: Male Higgins eye side. The inside of the shell is white extended as far south as St. Louis, release sperm into river currents with portions that are iridescent and Missouri and included several and females downstream siphon the areas that may be tinged with cream additional tributaries of the sperm to fertilize their eggs. After or salmon. The soft body enclosed by . fertilization, females store the shell consists of gills for developing larvae (glochidia) in their gills until expelling them back into breathing, a digestive tract for Habitat: The Higgins eye is a the current. Some glochidia are processing food, and a large muscled freshwater mussel of larger rivers able to attach to the gills of host fish, foot for moving and for anchoring on where it is usually found in deep where they develop further. After a the stream bottom. water with moderate currents. The few weeks, juvenile mussels detach animals bury themselves in sand and from the fish’s gills and settle on the Range: Since 1980, live Higgins eye gravel river bottoms with just the river bottom, where they can mature have been found in parts of the upper edge of their partially opened shells into adult mussels and possibly live Mississippi River north of Lock and exposed. River currents flow over up to 50 years. The sauger, , Dam 19 at Keokuk, Iowa and in three the mussels as they siphon water for , largemouth and tributaries of the Mississippi River: microorganisms such as algae and , and freshwater the St. Croix River between bacteria, which they use as food. drum are considered suitable hosts for Higgins eye glochidia. Minnesota and Wisconsin, the Higgins eye are prey for wildlife Wisconsin River in Wisconsin, and like muskrats, otters, and raccoons; Why is the Higgins eye the lower Rock River between Illinois they filter water which improves pearlymussel endangered? and Iowa. Recently, we successfully water quality; and mussel beds create reintroduced the Higgins eye into the microhabitats on river bottoms that Habitat Loss and Degradation: Higgins Iowa River and Wapsipinicon River provide food and cover for other eye depend on deep, free-flowing in Iowa. The current range is about aquatic life. rivers with clean water. Much of their historic habitat has been hard by colonization. Habitat Protection: A variety of changed from free-flowing river The Prairie du Chien, Wisconsin, government and private conservation systems to impounded river systems. population has been reduced from agencies are working to preserve Impoundments changed water flow one of the most numerous to one of Higgins eye and its habitat. patterns, substrate characteristics, the most threatened. Technology to and host fish habitat which, in turn, control zebra mussels is being Propagation and Reintroduction: Since affect how Higgins eye feed, live, and studied, but no successful measures about 2000, government agencies reproduce. Municipal, industrial, and have been developed that can reliably have cooperatively developed farm run-off degrade water quality. limit zebra mussel colonization and techniques to propagate Higgins eye As filter-feeders, mussels concentrate not harm native mussels. and reintroduce the captive bred chemicals and toxic metals in body mussels into rehabilitated habitats tissues and can be poisoned by What is being done to prevent in the Mississippi River and several chemicals in their water. Dredging extinction of the Higgins eye tributaries. and waterway traffic produce pearlymussel? siltation which can cover river What can I do to help prevent the substrate and mussel beds. Listing and Recovery Planning: The extinction of species? Higgins eye was added to the U.S. Exotic Species: Invasive zebra List of Endangered and Threatened Protect: Protect water quality by mussels are the greatest known Wildlife and Plants in 1976. As a minimizing use of lawn chemicals threat to Higgins eye. They are result of the listing, the U.S. Fish and (i.e., fertilizers, herbicides, and insec- a freshwater mussel native to the Wildlife Service prepared a recovery ticides), recycling used car oil, and Black and Caspian Seas that were plan that describes actions needed properly disposing of paint and other introduced into Lake Erie in the to help this species survive. The toxic household products. late 1980’s from ship ballast water Recovery Plan was revised in 2004 discharge. These small mussels to incorporate new information and Follow: When boating, please follow are less than 2 inches long, but tens address the more recent threat of any rules established to prevent the of thousands can colonize a square zebra mussels. spread of exotic pests like the zebra meter area. Zebra mussels attach to mussel. any hard surface, including shells of Research: Researchers are other mussels, preventing them from continuing studies of zebra mussels Encourage and Implement the use of normal travel, burrowing, and and their impacts on Higgins eye, of agricultural practices that minimize opening and closing their shells. commercial navigation impacts on the erosion of topsoil into rivers and mussels, and of water quality and streams and that moderate the flow Several Higgins eye populations in contaminant relationships to the of surface runoff – increased runoff the Mississippi River have been hit species. from agricultural lands is an important factor in the increased rate of sedimentation in the Mississippi River. Photo by Minnesota DNR; Bernard Sietman This female Higgins eye is buried in the river bottom with a portion of shell U.S. Fish & Wildlife Service and mantle exposed. The mantle looks like a small fish to attract larger fish. http://www.fws.gov/midwest/endangered When a fish approaches she releases her glochidia, which can then attach to the fish’s gills. Revised August 2012