Karen Terry, University of Minnesota Extension Service, Regional Extension Educator, 218-998-3927

Mussels are fascinating but can be hard to know because they spend most of their lives buried in the bottom of Minnesota’s lakes and streams. When people do happen to find them, they often call them clams, but mussels and clams are not the same. They are both mollusks, but the biggest difference is that mussels are capable of making pearls and clams are not. Minnesota’s clam species are very small, but our mussel species can be as big as dinner plates.

This giant floater is just one of Minnesota’s many native mussel species. Photo credit: MN DNR

Minnesota’s mussels have interesting names like spectaclecase, pistolgrip, heelsplitter, and wartyback. There are nearly 50 species of native mussels in Minnesota, but many of these are listed as endangered, threatened, or of special concern. One of the most imperiled groups of living things nationwide, mussels depend on clean water and diverse fish communities to survive. A healthy population of mussels is a good indicator of a healthy lake or river.

Mussels do not have eyes, legs, or fins. Throughout their lives, they move by floating downstream, hitching a ride on fish, or by anchoring with their ‘foot’ and pulling themselves along slowly. To reproduce, males release sperm into the water and the females draw it in to fertilize their eggs, which they brood internally. The females later release the tiny larvae, called glochidia, into the water. The glochidia then attach to a fish for the next stage of their lives. Many mussels require a certain species of fish to attach to, and if that mussel does not find that species of fish, then the glochidia will likely die. Glochidia that do latch onto the right fish attach to the fish’s gills, fins, or scales and live as parasites until they are old enough to drop off, settle to the bottom, and begin life on their own. Mussels live from 10 to 30 years.

This DNR mussel researcher is sorting mussels by species. After they are identified, they will be measured and recorded to create a list of mussel species in the water body. Photo credit: MN DNR

Native people used mussels for food, jewelry, and utensils. More recently, shells were used to make buttons for clothing, and they are still used in some places to make cultured pearls. Because mussels reproduce slowly, over-harvesting decimated many populations. Today it is illegal to harvest mussels in Minnesota.

To learn more about mussels, look for empty shells in the shallow water along shore. You can study the shell as long as you return it to the place you found it, but it is illegal to pick up live mussels without a permit. More information can be found in the small spiral-bound book, “Field Guide to the Freshwater Mussels of Minnesota,” available from Minnesota’s Bookstore, 651- 297-3000 or 800-657-3757.

Posted in Fish and Wildlife |