ST. CROIX FALLS, Wis. (WFRV) – Biologists found endangered mussels that are believed to be over 100-years-old in a river in northwest Wisconsin.

The Wisconsin Department of Natural Resources (DNR) announced that federal and state endangered native mussels that were first found above the St. Croix Falls dam in 1987 are still alive and believed to be over 100-years-old.

Back in Aug. 2021, biologists from the DNR, University of Minnesota and the National Park Service searched a stretch of river where the spectaclecase mussels were previously found 34-years-ago. The stretch of river was upstream of the St. Croix Falls Dam.

They reportedly found a cluster of the native mussels.

Due to the mussel shell erosion, officials were not able to figure out the mussels’ age on-site by counting their growth rings. However, they figure the specimens are over a century old based on when the river was damned.

“Native mussels can live a long time, but these mussels were pushing the limits. Finding some alive was amazing since the host fish species needed for their reproduction have been prevented from getting upstream as a result of the St. Croix Falls dam built in 1907,” said Lisie Kitchel, DNR Conservation Biologist.

  • Photo Courtesy of the WI DNR and National Park Service

The DNR says that after female spectaclecase mature they expel their larvae, which must attach to the gills or fins of a specific fish to continue developing into a juvenile mussel. Then they drop off the fish and grow into an adult mussel.

Wisconsin has 50 native mussel species, and 24 of them are endangered, threatened or in need of conservation. They also provide an important role in the ecosystem by filtering pollution from the water as well as providing food for multiple creatures.

More information about the mussels can be found on the DNR’s website.