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Home > Wildlife > Species Information >Maine Endangered Species Program > Endangered and Threatened Species > Invertebrate List > Yellow Lampmussel
The yellow lampmussel is a large (up to 4½-inch) freshwater mussel that superficially resembles a marine clam. Its shell is oval-shaped and distinctly yellow, occasionally with faint green rays. The nacre, or pearly lining of the inside of the shell, is usually white or bluish-white. This species can be confused with the tidewater mucket, which is of similar shape and coloration but usually has a bronze tinge in adult specimens. The structure and placement of the hinge teeth, plus color of the nacre, help to distinguish these two species. (For more detailed information on identification, see MDIFW's book, The Freshwater Mussels of Maine.)
The yellow lampmussel is found in Atlantic coastal drainages from Georgia to Nova Scotia. In Maine it is currently known only from the Penobscot, St. George, and lower Kennebec River watersheds. This species typically prefers medium to large rivers, but in Maine is often found in lakes and ponds, and will tolerate impounded sections of rivers. It occurs in a variety of bottom types, including silt, sand, gravel, and cobble.
Freshwater mussels have a curious way of reproducing that depends on the presence of fish. The yellow lampmussel breeds in late summer, when males release sperm into the water and females filter it out of the water with their gills. Once the eggs are fertilized, females brood the growing larvae, called glochidia, in a modified portion of their gills called a marsupium.
The following summer, each larvae-bearing female releases thousands of mature glochidia. At this stage, glochidia require fish hosts to change into the subadult form of a mussel. They can only survive for a short time on their own and must quickly encounter a suitable host fish. To aid the glochidia in finding a host, larvae-bearing female yellow lampmussels use a fleshy modification of their mantle (flap-like tissue lining the shell) that is shaped like a small minnow to attract fish. When a fish bites the lure, glochidia are released. They then attach to the fish's gills (without apparent harm to the fish) for a period of weeks or months before transforming into tiny mussels and dropping off to settle in the bottom. Each mussel species requires one or more specific fish species to serve as suitable hosts. Currently, known fish hosts for the yellow lampmussel are yellow and white perch.
Freshwater mussels grow rapidly during their first 4-6 years of life, before they become reproductively mature. Longevity of the yellow lampmussel is likely 15 years or more. Mussels continually filter vast quantities of water and consume bacteria, algae, and plant and animal debris. They burrow into the bottom and anchor themselves with a muscular foot. They have a limited ability to move slowly around the lake or river bottom to find the best sites for feeding and reproducing. Mussels are an important food item for some aquatic mammals, especially otters, muskrats, and raccoons, as evidenced by piles of shells (middens) often seen along shorelines.
Freshwater mussels are the most endangered group of animals in North America. Of the nearly 300 species native to North America, approximately 75 percent are state or federally listed as endangered, threatened, possibly warranting listing status, or already extinct. Their population declines are the result of more than a century of industrialization and development of our waterways, causing alteration and loss of habitat and degradation of water quality.
The yellow lampmussel has declined throughout its range and has been extirpated from many rivers in the Northeast. Habitat degradation and pollution have eliminated some populations. Unlike many species of mussels, however, the yellow lampmussel is able to survive in impoundments.
Another serious threat to native mussels is the exotic zebra mussel, which was accidentally introduced to the Great Lakes and is spreading across North America. It carpets the bottom of lakes and rivers, and out-competes native mussels for space and food. Although it has not been found in Maine, the zebra mussel could represent a major threat to yellow lampmussel populations if introduced here.
Population declines have been documented for the yellow lampmussel throughout much of its range, prompting many states to add it to their lists of endangered and threatened species. It also is a former candidate for federal listing. In 1997, the species was listed as threatened in Maine. It is known from only three watersheds in the state, and is usually found in low numbers at most sites.
Conservation of mussels requires identification and protection of their habitats, and suitable populations of their fish hosts. MDIFW completed a seven-year survey of the state's freshwater mussels in the 1990s. Populations of yellow lampmussels are well documented, and information is being provided to towns, land trusts, and lake and watershed associations. In 2001, research was initiated at the University of Maine to document the fish host(s), population size and structure, and genetic uniqueness of populations. Monitoring is needed to assess population trends, and additional life history studies are needed to learn more about the species' habitat requirements, reproduction, and interaction with fish host populations.
Maine may have some of the largest remaining populations of yellow lampmussels in the East, and will play an important role in the species' conservation. Protection of clean, unaltered watersheds and associated forested riparian areas is necessary for the long-term existence of this species. The yellow lampmussel shares much of its habitat in Maine with the tidewater mucket (threatened), shortnose sturgeon (federally threatened), Atlantic salmon (federally endangered), and other rare species like the brook floater (mussel), wood turtle, and New England bluet damselfly. Adhering to state wetland and Shoreland Zoning laws and water quality Best Management Practices contributes greatly to maintaining the quality of aquatic habitats for this species. Shoreland zoning and LURC zoning standards provide protection of habitat up to 250 feet from larger rivers. Some forest companies voluntarily extend the conservation of intact, forested riparian zones to 330-600 feet for larger rivers.
For more information contact Maine's Endangered Species Program at (207) 941-4466.
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