A mussel lays on the Namekagon Riverbed as water rushes past

Native Mussel Propagation

Working to save the Winged Mapleleaf Mussel

Land & Water Conservation
A person holds a winged mapleleaf mussel.

Playing a crucial role beneath the water's surface

Each of the 41 mussel species found here today was present in these two rivers before European settlement. Today, this remarkably diverse mussel community is a rare example of an intact group of river-dependent animals that has withstood the test of time and changing environmental conditions.

The St. Croix National Scenic Riverway is home to one of the only known self-sustaining populations of the winged mapleleaf mussel (Quadrula fragosa).

Why Native Mussels Matter

A single native freshwater mussel can filter between 5 and 15 gallons of water per day, with some reports indicating up to 18–20 gallons. They act as natural, powerful filters by removing algae, bacteria, sediments, and heavy metals from rivers and lakes.

a underwater shot of a channel catfish being released back into the river

Small Beginnings

Freshwater mussels have a complex life cycle that depends on a host, often a fish, for microscopic mussel larvae, or glochidia, to develop into juvenile mussels. In early fall, female Winged Mapleleaf mussels display a tissue lure to attract a host fish, and in the St. Croix only the channel catfish will do.

The glochidia released by the female mussel then attach to channel catfish gills where, over the next 7-8 months, they develop into juvenile mussels. Those juvenile mussels then detach from the host fish and fall to the riverbed as free-living mussels.

Native Mussel Propagation

Once thought extinct, a small population was discovered in the St. Croix River in 1987. The St. Croix River population is genetically distinct and the only one known to be reproducing.

While the existence of this reproducing population brought hope, the complex life cycle of freshwater mussels meant that innovation would be necessary to achieve a stable population.

A mussel lays on the Namekagon Riverbed as water rushes past

Special and fragile ecosystems

The St. Croix and Namekagon rivers are home to these freshwater organisms because of the variety of underwater habitats like boulder fields, gravel beds, sand bars, and mucky backwaters. The requirement of specific host fish, competition from exotic species and their need for free flowing, unpolluted rivers has resulted in the endangerment and extinction of many mussel species.

Helping their life cycle along

Our work consists of capturing female mussels, infesting catfish, over-wintering them at USGS in their tanks, then monitoring them in the trailer on the St. Croix. Once the juvenile mussels are large enough they are released into concrete mussel silos in the river for monitoring before being fully released

Innovative breakthrough

Over the past 17 years, efforts to propagate winged mapleleaf in hatchery and laboratory facilities have been limited due to high fish mortality overwinter while glochidia are attached and from high mortality of newly released juvenile winged mapleleaf held in the laboratory. The novel concept of using the trailer to pump the St Croix water into the holding tanks is what’s made the difference and allowed us to successfully propagate winged mapleleaf mussels.

Continued learnings and work

Each year of operation provides learnings for the partnership group.

Along with continued population monitoring, we plan to continue the only successful winged mapleleaf mussel propagation project in cooperation with UM Extension, USGS and NPS.

Partners

Center for Aquatic Mollusk Programs

A mussel lays on the Namekagon Riverbed as water rushes past

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