Mussels in Decline
Freshwater mussels play an important role in water quality and in aquatic health. A single freshwater mussel can filter half a gallon or more of water per hour. A freshwater mussel is different from other bivalves, including salt water marine mussels, because it requires host fish to propagate, and it lacks a means of attachment to secure it to underwater structures. The fertilized larvae of the freshwater mussel attach themselves to a fish, where for a few weeks as a short-term parasite, they can take up a tiny amount of blood from the fish. The muscle larvae are so small that they do not hurt the fish during this time. And that short parasitic relationship is all they need to metamorphose into a small mussel and then develop over the next 5 to 7 years into an adult. Mussels are among the most long-lived animals, with life spans up to 100 years.
Many of the approximately 300 species of mussels in the US are declining, with the most endangered ones requiring specific fish species to complete their life cycle. Some mussels are tied to host-parasite relationships with declining migratory fish like shad and herring. The most prevalent mussel in Maryland, the Eastern Elliptio (Elliptio complanata), has declined from several pressures, including excess runoff from development and farms and the influx of invasive species like the rusty crawfish and Asiatic clam. The Eastern Elliptio lives in Maryland surface waters from Allegheny County east.
Maryland and local efforts to reduce sedimentation, nutrient and chemical influx into surface waters are mainly publicized concerning restoration of the Chesapeake Bay. The same improvements to the environment are helping to restore our freshwater aquatic wildlife, including the lowly mussel.
In our area, the Atlantic Ribbed Mussel (Geukensia demissa) is harvested as seafood. These marine mussels are prevalent in the mud flats and estuaries of the middle and lower Chesapeake Bay. Although it is often thought that the mussels sold for food in the US are freshwater varieties, the ones that are widely enjoyed as seafood are principally marine varieties.
Nature Note for 6/4/2017