St. Croix River Feasibility Study: Endangered Mussel Conservation

U.S. Army Corps of Engineers, St. Paul District
Published Feb. 27, 2015

Zebra mussels (Dreissena polymorpha) in the Upper Mississippi River are a significant threat to the endangered winged mapleleaf mussel (Quadrula fragosa) (WML). Management of zebra mussels may include measures to reduce/manage zebra mussels already present and prevent future spread of zebra mussels and/or other exotics. Alternatives considered in the Feasibility Study and Environmental Assessment included large- and small-scale alterations of the habitat conditions, closing portions of the system to recreational and/or commercial traffic, cleaning/coating technologies, barriers to prevent transport of zebra mussels, relocation of winged mapleleaf, juvenile seeding of winged mapleleaf and modification of reservoir operations to improve WML habitat.

The U.S. Army Corps of Engineers, St. Paul District and the Engineer Research and Development Center conducted a study in cooperation with the U.S. Fish and Wildlife Service, the National Park Service, the Departments of Natural Resources from Minnesota, Wisconsin, and Iowa, and the Great Lakes Indian Fish and Wildlife Commission. The Nature Conservancy has signed a Letter of Intent to be a non-Federal sponsor to conduct WML artificial propagation field work.


A feasibility study for the management of zebra mussels in the St. Croix River and connecting Mississippi River pools began in 2006.  A risk-based model was developed to evaluate likely pathways for further zebra mussel invasion, estimate long-term population characteristics and identify sensitive areas and potential ecological consequences.  Zebra mussels pose a threat to the already endangered WML mussel.  Management actions have been identified for relocations and artificial propagation of WML mussels. 

The Corps held public meetings in the St. Croix River Basin to assist in the development of identified management alternatives for zebra mussels and WML mussels.  The Corps, in cooperation with the Mussel Coordination Team, identified suitable reintroduction sites for WML mussels.  Genetic studies of the species provided guidance on establishing new WML mussel populations.  Life history studies of the species have identified host fish species and reproductive requirements to facilitate artificial propagation.  A draft report was completed in October 2013, and a final draft report was completed in late 2016.  This study was terminated in September 2017.


The study is being conducted under the authority of Section 216 of the Flood Control Act of 1970 and in conformance with the final Biological Opinion for the operation and maintenance of the Upper Mississippi River 9-foot navigation channel, which recommended a feasibility study at full Federal expense. 

Feasibility Study 2006-2017
Through FY2017  $1.8 million
Balance to complete $49,000
Estimated cost (100% Federal) $2.3 million

Recommended Implementation Costs- 10 Years
Federal cost for field work $2.75 million
Non-Federal Cost $1.43 million
Total Estimated cost                              $4.18 million