Frequently asked questions about freshwater mussels:

Q. Why are freshwater mussels important?

• They are ecological indicators. When you find freshwater mussels, you can be pretty sure the water quality in the area is good!
  
• They are important food source for many animals, including muskrats, minks, otters, fishes, and some birds.
  
• Freshwater mussel tissues have resistant or slow cancer growths. Biomedical researchers have been studying why.
  
• Mussels are also harvested in the south where they are shipped to Japan for the pearl industry.
  
  
  

Q. What is the difference between a native mussel and the zebra mussels?

A. Native mussels are in a group, or family called "Unionidae". In general, unionids are much larger than the zebra mussels. Unionids have a larval stage, called a "glochidia" (which rhymes with the name "Lydia"). The glochidia must attach to the gills or fins of a fish to transform (or "metamorphose") into juvenile clams. Zebra mussels (scientific name Dreissena polymorpha) were probably introduced into Lake St. Clair in 1986, most likely from the ballast water of a Great Lakes ship. A single female of a unionid mussel and a zebra mussel can produce several thousand eggs per year. However, zebra mussels don't have a parasitic stage. Since they don't need this extra step to become adults, populations are able to grow and survive at a greater rate than the native mussels.

Q: Do the glochidia harm the fish?

A: Not really. There are a few records of fish in a hatchery being harmed, but this was under unnatural conditions. The glochidia may actually help the fish develop an immunity to other harmful parasites, but this has not been studied extensively.

Q: What is the difference between a mollusk, a bivalve, a clam, a mussel and a naiade?

A: A mollusk includes everything in the phylum Mollusca, from slugs to squid to clams. A bivalve, mussel, and clam are basically the same thing--mollusks with two valves. Naiades are freshwater mussels in the family Unionidae.

Q: Do people eat freshwater mussels?

A: Not today. Native Americans not only ate them, but used them for tempering pottery and making utensils, tools, and jewelry.

Q. Why do zebra mussels harm the native mussels?

A. Zebra mussels attach to the native clams by use of byssal threads. Some people have counted thousands of zebra mussels on one clam! All this weight makes it very difficult for the native clams to move. The zebra mussels filter the water around the native clams, which may also starve the native clams.

Q. I've heard that many freshwater mussels are in trouble. Is this true?

A: Yes. North America has the most diverse fauna of unionid clams in the world. Unfortunately, they are now one of the most imperiled groups of animals. Of the almost 300 species recognized in North America, 13 are considered extinct, 44 are recognized by the U. S. Federal Endangered Species Act, and about 60 are under consideration for federal listing. Unionid clams have been declining throughout the United States because of water quality problems caused by dredging, damming, and pollution, decline of their fish hosts and most recently, the zebra mussel invasion.

Q: What can we do to help the mussels?

A: Work to preserve water quality. If you have a boat that you use on both the Great Lakes and inland lakes, make sure your boat is free of zebra mussels before launching it on an inland lake.

Q: How many species of unionids are there in Michigan?

A: Fourty-six. You can view these on our list

Q: Are there other kinds of native freshwater clams in Michigan?

A: Yes. Other clams commonly found are the pill or fingernail clams. These are in the family Sphaeridae. As the name implies, they are about the size of your fingernail.




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