Freshwater Mussels of Iowa

Photo by Chris Wendel 

Freshwater mussels are known as bivalves (mollusks with two shells). They live in the lakes, rivers and streams of Iowa. Currently Iowa has 42 species, down from an original count of 54.  North America has approximately 300 species of mussels. In Iowa, nine mussels are endangered and six are now threatened.  Currently, mussels are the most imperiled animal across North America and deserve our protections. The most species exist in the mid-western states but are in decline here as well.

Mussels are an indicator of water body health and are vulnerable to poor water quality due to pollution, sedimentation and impairment.  Dams can also prevent travel of host fish species, thus trapping the species dam to dam.  Mussel populations improve when dams are removed.

Mussels are very tough, temporarily in impaired waters and are great at water filtering with an average of 9 to 10 gallons of water per day per mussel being filtered. It makes sense to help and conserve them so they can help purify our 750 impaired rivers and waterways of Iowa. They can be very long lived, living 10 to 100 years in the right conditions.  They develop growth rings on their shells similar to tree rings.

Mussel babies called Glochidia, get attached to their specific host fish by assorted methods by the female mussel. They live on the gills and fins of fish for weeks or months, then are released to the water body bottom to live out their life filtering water and enjoying the nutrients that float by.  They will not travel far during their lifespans and sometimes you can see their path in shallow water.  If you see one in shallow water, it makes sense to move them to deeper water. Do not try to bury them, let them place themselves back into their preferred position.

Many river animals rely on mussels for food. They are muskrats, mink, otters, raccoons, turtles, fish and birds like crows, geese, egrets and heron.  As a result, you will see many dead shells on banks, sand and gravel bars.

During the early 1900’s mussels were over harvested due to the large pearl button industry in Iowa. Buttons were punched out of shells creating blanks that became buttons.  Button factories were located in Lansing, Muscatine, Guttenberg and many along the Iowa river. Over harvesting lead to much mussel decline.  As a result, laws were created and plastics replaced the pearl button craze. There still exists mussel poaching, with shells being sent to the Japanese cultured pearl industry.

It is best to not collect or dig out these vulnerable species and instead, enjoy looking at and comparing dead mussel shells on sandbars while you recreate. It is illegal to possess live or dead threatened or endangered mussels of Iowa. Stiff fines up to $50,000 can result. Mussel species are difficult to identify, so be careful if you do.