Minnesota is home to many species of native freshwater mussel.

Freshwater mussels, what many people often refer to as ‘clams’ here in Minnesota, are some of the most imperiled animals on the planet. And the health of our lakes and rivers depend on native mussels which act as natural cleaners, filtering the water and creating habitat for many other wild animals.

Minnesota was historically home to 50 species of native mussels in our lakes and rivers but today many of those can no longer be found, and those that remain face an uncertain future. Historic over-harvesting for the button industry, the construction of dams, pollution, and invasive species have impacted our native mussel species and subsequently the health of our waterways.

In partnership with the Minnesota Department of Natural Resources (DNR), biologists at the Minnesota Zoo have been raising native mussels to repopulate our lakes and rivers.

The lifecycle of freshwater mussels is unique and fascinating and has necessitated much ingenuity from the scientists studying them. As young larvae, mussels require a fish host in order to grow large enough to live on their own at the bottom of a lake or river. They attach to the gills of a fish, such as walleye, and after they have completed development, they are released to the sand and pebbles below. These hitchhikers do little to no harm to their fish host and in turn are often transported a great distance from their original birthplace by the roaming and unsuspecting fish. As if this wasn’t complicated enough, for some mussels like the Salamander and Spectaclecase, there are only one or two specific fish species that can act as a host.  In some cases, scientists are still trying to discover which hosts pair with mussels that are in need of restoration. Understanding this connection can make lab rearing possible and can help conservationists understand what fish species may need recovery, too.

Walleye raised at the Zoo before being inoculated with mussel larvae and released.

In recent years, groups of walleye, which are a common fish host, have been reared at the Zoo until they are large enough to carry their first group of tiny mussels. Earlier this fall, dozens of walleye were transported from the Zoo down to the Cedar and Cannon Rivers where they were inoculated with Mucket mussel larvae and then released into the running waters to greatly increase the number of mussels in those watersheds this year.

Alongside the walleye, hundreds of freshwater mussels which had been reared by the DNR over the past few years were tossed (literally) into the river. The expectation is that both the walleye and the mussels will thrive in their new environments, each helping the other out and together creating a more resilient and robust underwater world.

Adult mucket mussels before being released into the Cedar River.

Freshwater mussels are an integral part of healthy freshwater systems. They help clean water, encourage plant growth, create habitat for other species, and stabilize sediment. Unfortunately, by many estimates they are the most at-risk group of animals in North America which makes the restoration efforts by the Zoo and DNR so important.

Zoos and aquariums across the continent have united for the conservation of these species and recently launched the new SAFE North American Freshwater Mussel initiative. Hosted by the Association of Zoos and Aquariums, SAFE (Saving Animals from Extinction) programs leverage the combined resources of participating institutions to create impactful conservation programs for animals in the wild. The new freshwater mussel SAFE program will focus on the urgent need for more research, restoration, and education to help save these vital animals from extinction.