What are Freshwater Mussels?

There are around 1,000 species of freshwater mussels in the world, and over 300 of them are found in the United States. These mussels look similar to the saltwater variety and can vary greatly in size. They can be found all over but are most commonly in streams and rivers. The Tennessee River drainage basin has a particularly diverse array of freshwater mussel species. In fact, there are over 100 mussel species in this basin and more than 40 of them are not found anywhere else in the world. Virginia’s Powell, Clinch, and Holston rivers all make up part of this basin.

Just like their saltwater cousins, freshwater mussels are filter feeders. They live on small particles of bacteria and algae that are suspended in the water. This feeding process results in them acting as a natural filter for the waterway. These animals are extremely important to the ecosystem because of this cleaning service they provide.

In addition to improving water quality, mussels also play several other important roles in the ecosystem. Microorganisms and plants inhabit the outside of the shells. Mussels themselves are a food source for many different types of animals. Finally, the shells of dead mussels are often used as shelter by fish and other aquatic life.

How Do People Use Freshwater Mussels?

People have used freshwater mussels for centuries. They served as a food source for Native Americans and the shells were frequently used as jewelry. In more recent times (early 1900’s) the shells were used as buttons on clothing. In fact, many freshwater mussel populations were decimated due to over harvesting for making buttons. The main use for them nowadays is as the filler material for making pearls. Tons of freshwater mussels are harvested and shipped to Asia for this purpose every year. In some cases they are even being illegally harvested.

Mussel Life Cycle

Freshwater mussels have a very interesting lifecycle. Many people don’t realize that mussels are actually parasites at one point in their lives. The male mussels fertilize the eggs in the female mussels through the use of the river current. The eggs then develop into larva called glochidia while they’re still attached to the female. The female organizes them into a lure-shaped structure to attract certain species of fish. For many mussel species there are only a select few species of fish that will work for this process. The mussel releases the glochidia when the fish approaches. The larva then attach to the fish gills or fins and embed themselves in the fish tissue. The glochidia at this stage are still microscopic in size. They live as a parasite in the fish tissue for several weeks while they continue to develop. During this period they grow their foot muscle and the rest of the internal structure. They then drop off the fish to find an anchor point to attach themselves to. The fish plays a critical role as a temporary host and as transportation away from the mussels parents to new areas of the waterway. This helps with species survival and genetic diversity.

Can You Eat Freshwater Mussels?

Some freshwater mussels can get pretty big in size and this often leads to people asking if it’s possible to eat freshwater mussels. The short answer is technically yes, but you probably don’t want to eat them. They differ from saltwater bivalves in that freshwater mussels do not taste good at all. Not to mention there could be some serious health concerns associated with eating freshwater mussels. The filter feeding process can lead to mussels collecting toxins from the water and most rivers around the country have at least one type of pollution concern.

What’s Happening to Freshwater Mussels?

Freshwater mussel species are diminishing at an unprecedented rate for a variety of reasons. They are one of the most critically endangered species in the country. More than 70% of the freshwater mussel species native to North America are either endangered or have already gone extinct. Sediment runoff, agricultural pesticides, and other sources of chemical pollution are devastating the native freshwater mussel populations around the country. Excessive sediment in the water can settle on the bottom and smother existing mussel beds. The sediment also covers the natural rocky bottom which prevents mussels from finding suitable anchor points. The mussels also depend on certain fish species, so, when the fish is threatened by habitat loss, dam construction, or pollution, the mussels aren’t able to reproduce. These bivalves can often serve as indicator species for the overall health of a freshwater ecosystem. 70 percent of the 82 freshwater mussel species native to Virginia are in decline.

What’s Being Done?

The good news is that people are aware of both the importance of freshwater mussels and their alarming population decline. Virginia set up the Aquatic Wildlife Conservation Center (AWCC) to breed freshwater mussels. The entire system is run the same way a natural ecosystem functions. So they have various fish species in the mussel tanks to serve as temporary hosts for the glochidia. The Department of Game and Inland Fisheries releases these mussels into streams every year to help bolster the native populations. You can help freshwater mussels by limiting the use of pesticides in your yard and planting trees near waterways to reduce sediment erosion.

Sources: Virginia Department of Game and Inland Fisheries
U.S. Fish and Wildlife Service