Almost 300 freshwater mussel species are described in North America, and more than thirty kinds live in South Carolina. The United States contains the greatest number of freshwater mussel species in the world, and the majority of the diversity is concentrated in the Southeast. Unfortunately, these aquatic animals may be the most troubled group of species in the United States.
"According to the American Fisheries Society, over 47 percent of the species in the United States and Canada are considered to be endangered, threatened, or possibly extinct and many of these mussels are not federally or state listed with an official status," said Jennifer Price, S.C. Department of Natural Resources biologist. Seventy species are federally listed as endangered or threatened. "The exact number of described species is often changing. We are working on revising the status of several species, and discovering new species in bodies of water that have not yet been well-surveyed." Price said that much remains unknown about the biology and population dynamics of mussels, or how commercial exploitations and human-induced environmental changes impact these animals.
Contact Price via e-mail at PriceJ@dnr.sc.gov or call (803) 353-8232 for more information on freshwater mussels and research in South Carolina.
Mussels are important indicators of water quality and are extremely sensitive to changes. Some have been documented to live as long as 100 years. The presence of a mixed population of healthy aquatic insects, mussels and/or fish usually indicates that the water quality has been good for some time. Furthermore, many animal species (such as muskrat, mink, otter, and some fish species) feed on freshwater mussels, and other organisms use remnant shell material for shelter or spawning substrate.
Historical accounts indicate that most South Carolina streams and rivers were covered in mussels from bank-to-bank in the 1700s, but now many rivers have none. The Carolina heelsplitter, a federally endangered species, was rediscovered in 1987. It had not been found alive since the mid 1800s. The heelsplitter has been reduced to only eight known surviving populations: two in North Carolina and six in South Carolina. The complete historic range of the species is unknown, but there is always the possibility more will be discovered.
"The heelsplitter, along with all other mussel species, is vulnerable to a variety of threats related to human disturbance," said Price. "Pollution from wastewater from sewage treatment plants and industrial discharges are a threat. Storm water runoff carrying silt, fertilizer, pesticides and other pollutants threatens the Carolina heelsplitter, especially when erosion and stormwater control is inadequate."