Maine's Freshwater Mussels

Freshwater mussels are are a valuable indicator of water quality and aquatic ecosystem health. They are long-lived - more than 100 years for some species. These molluscs are one of the most imperiled groups of animals in the country - of the nearly 300 species of freshwater mussels found in the U.S., more than a third have already vanished or are in danger of extinction; over 75% are listed as Endangered, Threatened, or Special Concern on a state level. These dramatic declines have been caused largely by the degradation and loss of mussel habitat from pollution, dams, and the channelization and sedimentation of once clean, free-flowing rivers and streams.

Of Maine’s 10 native species, three (Yellow Lampmussel, Tidewater Mucket, Brook Floater) are currently listed as Threatened under the Maine Endangered Species Act and one (Creeper) is considered of Special Concern. The Yellow Lampmussel and Tidewater Mucket are listed because of their restricted distribution in Maine – both are found only in the Penobscot, St. George and lower Kennebec River watersheds. The Brook Floater is one of the rarest freshwater mussels in the Northeast. Fortunately, compared to most states within the range of these rare mussels, Maine hosts some of the best remaining populations and may be a last stronghold.

(Text adapted from MDIFW Freshwater Mussels web page. Data for this map courtesy of B. Swartz, MDIFW, 2016. Data set may be viewed HERE.)

Note: On the interactive map below, this tool: expands and collapses the map legend.