Mussels in Our Streams Mean Waterways Are Clean

Updated: Aug 18

Mussels are interesting and important creatures, but they are often overlooked. More than 80 different types of mussels used to live in freshwater rivers, lakes and ponds in Illinois. Now, 59 species remain in our state. Some of the mussels live in only one single stream.

An ellipse mussel. (Photo by Angela Rafac)

The ellipse mussel is an uncommon freshwater mussel in our rivers. Their favorite habitat is small- to medium-sized streams with clear waters. They like a sandy and gravely bottom or a mixture of both. Most often, ellipse mussels are found in riffles and runs. A riffle is a shallow part of a river where the water runs quickly as it swirls and spins over the rocky bottom. Runs are deeper parts of rivers where the river flows smoothly but quickly.


What is a bivalve?


Mussels are a type of bivalve. They have two hard shells on the outside and soft parts on the inside. The knobby part at the base of the shells is called the umbo or beak. To the right is the hinge. Mussels spend most of their time with their bottom shell buried in the ground.

A mussel’s shell grows larger as it gets older. Shells can have different shapes, sizes, colors and thicknesses.

(Photo by Angela Rafac)

The ellipse mussel is named after its oval shape. Fully grown, these mussels will reach about 3 inches in length. Their shells are smooth on the outside and thick for their small size. One of the most distinguishing features of the ellipse mussel are the beautiful green rays that start at the base and spread to the outer edge of the shell.


To eat and be eaten


Mussels are filter feeders, so they pull in water and absorb tiny organic particles like algae, bacteria and plankton. They help clean the water when they eat. They have gills inside their shells so they breath dissolved oxygen just like other underwater animals.


Predators of mussels include raccoons, muskrat and mink. They will dive into the water and search for mussels at the bottom. They pry them open and eat the soft insides. Sometimes you can find the shells they leave behind along the water’s edge. If it was eaten by the same animal, the right and left sides of the shell will fit together like puzzle pieces.


Baby mussels


Mussel babies would not survive without the help of a host fish. The clever mother mussel often uses a lure to attract fish, just like a fisherperson uses a lure. The ellipse mussel uses a simple lure to attract fish. In some mussels, the lure can look exactly like the host fish’s favorite food.

Words to know


Riffle: A shallow part of a river where the water runs quickly.

Bivalve: An aquatic animal with a compressed body enclosed within a hinged shell.

Once the fish comes close enough, the mother shoots the mussel babies, called glochidia (glo-ki-dē-uh), toward the fish. The glochidia use their tiny shells to clamp on to the fish’s gills. They hang on for awhile, hitching a ride, and eventually drop off to start their lives in a new location.


This process does not harm the fish. Different types of mussels depend on different types of fish. The ellipse mussel favors mottled sculpin, sunfish, saugers and drum fish.


A clean habitat


All mussel species rely on clean and healthy river habitats. The ellipse mussel is no different and has become less and less common as humans have changed the shape of rivers and polluted them.


The Forest Preserve District of Will County works to restore waterways to their natural shape and helps to clean them. In fact, a rare ellipse mussel was recently found in a stream that the Forest Preserve District worked hard to help!


You can help them too!


By doing your best to conserve water when you can and helping reduce water pollution you can help all mussel species, including the beautiful ellipse mussel.


Want to learn about the many ways you can help conserve water? Check out the U.S. Environmental Protection Agency’s WaterSense for Kids webpage.


To help reduce water pollution, don’t use the toilet like a wastebasket. Grease and oil from cooking shouldn’t go down the drain or be flushed away. They can be collected in a jar, and once the jar is full it can go in your regular garbage. Also, never flush old medications down the drain! There are places in Will County where you can drop off unused medications to be disposed of safely.

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