DESCRIPTION: Freshwater mussels are bivalve mollusks that have a two- valved hard shell, a soft body with respiratory, digestive and reproductive organs, and a muscular foot for locomotion, burrowing and orientation. The shiny layer inside the shell is called the nacre, or mother of pearl.

HABITAT: Freshwater mussels live on river bottoms and most require clean, flowing water to survive and reproduce.

RANGE: Worldwide, there are an estimated 1,000 species of freshwater mussels, about one-third of which occur in the United States. The vast majority of U.S. mussels are found in the southeast, with more species being found in the Tennessee and Mobile River basins than anywhere else on Earth.

MIGRATION: Adult mussels are largely sessile, rarely moving far along the river bottom. Larvae and juveniles are carried downstream by river currents and can be carried upstream on the gills of their host fishes.

BREEDING and LIFE CYCLE: Females lay eggs and brood them inside chambers in their gills called marsupia. Females draw sperm in through their siphons after males release their sperm into the water. The fertilized eggs develop inside the female into tiny larvae called glochidia. The glochidia must attach to the gills of a host fish or salamander to complete development. Some mussels produce lures to attract fish,? others trust chance and release their glochidia into the water column, and others package their glochidia into free-floating packets called conglutinates that look like prey items to infect fish that try to eat them. After a few weeks, perfectly formed tiny mussels drop off the gills and if they land in suitable habitat, than a new bed of mussels will grow bringing into being the next generation. Most mussels live around 60 to 70 years in good habitat.

FEEDING: Mussels feed by filtering algae, bacteria, phytoplankton and other small particles out of the water column. They are in turn preyed upon by fish, reptiles, amphibians, birds and mammals.

THREATS: Water pollution, runoff and sedimentation, dams, invasive species, overcollection.

POPULATION TREND: Nearly 70 percent of U.S. mussels have undergone population declines, with some species experiencing declines of more than 90 percent.






James spinymussel photo courtesy USFWS