Freshwater mussels are not high on the “cute” list of wildlife, but they play an important role in our ecosystem nonetheless. They are what’s termed indicator species which means they help indicate sources of clean water. They live in our freshwater streams and tributaries and filter the water as they feed. If the water becomes too polluted or toxic, they die which is happening more and more each year. Plus, as our population grows, development expands into areas resulting in habitat loss for the mussels since we have this need to move or reroute anything in the way. We also have an invasive species, the Asiatic mussel, which reproduces at a much more aggressive rate and overruns the mussel habitat. Therefore, our native mussels have become an endangered species on the brink of extinction.
Our folks in the Department of Natural Resources (both South Carolina and North Carolina) have been hard at work in restoring the freshwater mussel. Just recently, the SCDNR made the news when they successfully propagated 131 adult Carolina Heelsplitters with a known population in Lancaster County, SC. These mussels are tagged so they can be studied to determine their success.
The mussel propagation process is quite complex and I was fortunate to attend a session at a Fish Hatchery near Marion, NC to learn about what’s involved. I won’t bore you with all the details but it’s an interesting topic. First, the mussel requires a fish host for its eggs so the hatchery must grow certain fish species for this purpose. In the natural world, the fish is not harmed by being a host but they can die if there are too many mussels for the number of fish in an area so a balance is necessary. The mussel has a really amazing lure technique for attracting fish so they are able to disperse their eggs.
The freshwater mussel has several different methods for luring their fish host. Since they have no eyes they depend on water current and motion to trigger the lures. When they become sexually mature, about 3 years, during the spawning season, the females grow a lure that resembles a fishing lure on top of their shell.
This lure attracts fish since they think it’s food. When this happens, the mussel releases its eggs (in the glochidia or larvae stage) which attach to the fish gills and fins. From there, the mussel grows and feeds as the fish goes about its business. When the mussel reaches the juvenile stage it drops off the fish and starts its own journey to adulthood. Realize that a mussel is only a millimeter or so in size even after a year in a hatchery. It can take up to 5 years to have mussels large enough to release into the natural world.
The Carolina Heelsplitter is just one of several mussel species in danger. The Appalachian Elktoe and Tar River Spinymussel are others. But with the help of our DNR researchers and scientists, there is hope.
- 12,000 Tar River Spinymussels ( Elliptio steinstansana) were successfully propagated in the Upper Tar River Basin in Halifax County, NC
- 389 Carolina Heelsplitters (Lasmigona decorata) propagated in Goose and Duck Creeks in Union County, NC; 131 in Lancaster County, SC
- 4430 Appalachian Elktoe (Alasmidonta raveneliana) stocked in the Cheoah River NC with 20,000 more planned plus another 1300 for the Pigeon River near TN
For further reading, check out these sources: