Divers Remove, Relocate Endangered Species of Mussels from St. Croix River

News about the St. Croix River Crossing from the Minnesota Department of Transportation: 

Divers with the Minnesota Department of Natural Resources completed removal and relocation of more than 4,000 rare and endangered mussel species from the St. Croix Crossing worksite.

The freshwater mussels–including specimens of the rare Higgins eye mussel–were relocated during a two-week period as part of preparations for the earliest bridge work. Without moving the mussels, the work could have threatened their habitat on the river shores.

Efforts included locating, identifying and tallying each distinctive mussel species. The Minnesota Department of Transportation contracted with divers from the Minnesota DNR after several rare mussels were found in fall 2012.

The process involved divers crisscrossing an area about 75 feet by 400 feet along the Wisconsin side of the river to locate any mussels. Crews documented and etched a number into the shell of each Higgins eye found. Minnesota DNR divers will check on the relocated clams again in roughly a year to assess how they survived the move.

The Higgins eye mussel is on the federal endangered species list. Recovery efforts for this species have been in place since 1972, when federal funding for their protection and recovery was first appropriated. In the early 1980s, a team formed from the Minnesota and Wisconsin departments of Natural Resources, numerous local colleges and universities as well as other state and federal agencies to create a recovery action plan for populations of the mussel in Minnesota and Wisconsin.

The St. Croix River is considered one of the most important and biologically diverse refuges in America for native mussels. The St. Croix Crossing Project is committed to ensure protection of the mussels and other environmental factors.