Biologists discover rare mussels in St. Croix River

MADISON, Wis. (AP) — Biologists have discovered a cluster of rare mussels that could be more than 100 years old in the upper St. Croix River.

Wisconsin Public Radio reported Wednesday that biologists from the University of Minnesota, the Wisconsin Department of Natural Resources and the National Park Service discovered eight spectaclecase mussels in the river in August.

Biologists said the find was surprising because a hydroelectric dam built in 1907 divided the river and has prevented the host fish the mussels need to reproduce from reaching the upper stretches.