Eel River Watershed Initiative - Freshwater Mussels

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Often referred to as clams, freshwater mussels are intriguing animals that live in our rivers, lakes and streams. The United States has the greatest diversity of freshwater mussels anywhere in the worrld, and includes approximately 300 species and sub-species. However, freshwater mussels have become the most endangered group of animals on earth today.


You might be wondering why freshwater mussels became so endangered. There is a combination of events that has resulted in the depleted state of freshwater mussels. Historically, freshwater mussels have been used in many different ways, their shells were used for tool making, for food, and as decorative materials for Native Americans and early European arrivals. This low level of pressure on freshwater mussel populations was sustainable, for there was a thriving mussel population in our rivers and streams.

It all began when it was discovered that several species of freshwater mussels held a treasure inside them, the freshwater pearl. It is not unusual for pearls to develop inside freshwater mussels, in fact it is a natural reaction for mussels to create a pearly nacre around a grain of sand, or some other such irritation, that has made its way into the mussel. Tons and tons of mussels were harvested in search of pearls and easy riches during the Depression. After the Depression, freshwater mussels became more difficult to find and harvest, consequently there was a decline in the hunt for freshwater pearls.

Following the boom of the search for freshwater pearls, it was discovered that freshwater mussel shells made a beautiful button for the clothing industry. Button factories were opened near large rivers, and new harvesting methods were developed. Milions and millions of tons of mussel shells were harvested for the making of buttons. Thankfully, after WWII, plastic was developed that was much cheaper and tougher than freshwater mussel shells. Consequently, freshwater mussel harvesting for button making died out in the later part of the 20th century.

One remaining blow to the population of freshwater mussels was yet to follow. It was discovered that freshwater mussel shells provided the perfect seed material for synthetic pearl making. A tiny sphere of a freshwater mussel shell inserted into an oyster, caused the oyster to grow a pearl. While natural freshwater pearls varied in size and shape, the growth of synthetic pearls could be controlled.

The combination of these pressures over time has dramatically impacted the population of freshwater mussels in the United States. It has resulted in a ban on the harvesting of freshwater mussels in many states, including in Indiana. Since 1991, it is illegal for a person to be in possession of a freshwater mussel shell, weather is is alive or dead.

The Eel River has been home historically to 29 species of freshwater mussels. Currently we have documented 14 species living in the Middle Eel River, one of which is a state endangered species. Please see the posting from our website last year that demonstrates our escitment and appreciation of these incredible animals.


Maxwell Mattern and Kyle Boone, Manchester University 2012 Summer Interns, came upon a very rare sighting in the Eel River near Liberty Mills on Thursday, May 31st. A freshwater mussel displaying. The mussel has been identified as a Lampsilis cardium (Plain Pocketbook). The display is a part of the mussel's body mimicing the appearance of a small fish. This is an attempt to draw a host fish species (bluegill, largemouth or smallmouth bass) in close enough so that the adult mussel can release her glochidia (young parasitic mussel larva). The glochidia require a host fish in order to survive to maturity. These larval mussels attach the gills of the fish and obtain nutrients from the fish until they are mature enough to survive on their own, at which point they release from the fish gill and settle on the bottom of, or actually down inside, the stream substrate (bottom). It is a fascinating life cycle and one that we are often unable to witness due to the high levels of suspended sediment common in the Eel River in the spring. This very dry year has allowed us to watch this amazing natural phenomenon! The video below was shot by Maxwell Mattern. Just click on the picture below to see the video.

If you would like more information on freshwater mussels, here are some links you may enjoy the following websites and/or books:

The Freshwater Mollusk Conservation Society

United States Fish and Wildlife Service

Illinois Natural History Survey - Prairie Research Institute

The Freshwater Mussels of Ohio (On-lIne pdf Book)