Mississippi River mussel cleaning provides ecological and operational benefits

Photo By Melanie Peterson | Dan Kelner, fisheries biologist, relocates mussels in the footprint of a future cofferdam in the Chippewa River diversion channel, near Watson, Minnesota, August 4, 2020.  

ST. PAUL, MN, UNITED STATES

09.15.2021

Courtesy Story

U.S. Army Corps of Engineers, St. Paul District

Each year, for almost 20 years, the Corps of Engineers and other resource agencies on the Upper Mississippi River take a day and clean native mussels free from zebra mussels. No, they do not use scrub brushes, soap and water – just a little elbow grease.

Between 1998 and 2000, the Corps and the U.S Fish and Wildlife Service, or USFWS, were involved in formal consultation under Section 7 of the Endangered Species Act. The consultation focused on the Higgins eye pearlymussel and impacts from operation and maintenance of the existing 9-foot navigation channel for another 50 years.

Zebra mussels, transported by towboats and other large craft to upstream areas on the Upper Mississippi River using the federal navigation system, were a primary concern because they harm native mussels by smothering them and interfering with respiration, feeding and reproduction.

In its April 2000 Biological Opinion, the USFWS determined the operation and maintenance of the 9-foot navigation channel for an additional 50 years would jeopardize the continued existence of the federally endangered Higgins eye pearlymussel because it provides a steady upstream transport of zebra mussels on the river.

To avoid a jeopardy decision, USFWS recommended the Corps establish new populations of Higgins eye pearlymussels within the species’ historic range in areas with no or few zebra mussels and implement a zebra mussel control program.

The Mussel Coordination Team, or MCT, was formed to assist the Corps in complying with the terms and conditions of the 2000 Biological Opinion. The MCT includes malacologists – scientists who study mollusks – from the Corps’ St. Paul and Rock Island Districts, USFWS, U.S. Geological Survey, National Park Service, state departments of natural resources, universities and non governmental organizations.

Over the years, the MCT evolved from an oversight group into an award-winning team dedicated to freshwater mussel conservation on the Upper Mississippi River. Since 2000, the Corps has spent more than $8 million on a variety of mussel relocation activities with assistance from the MCT. This has involved propagating Higgins eye pearlymussel and placing them in waters not infested with zebra mussels. The plan used a combination of five propagation and relocation methods at 10 sites to reach the goal of at least five new populations in 10 years that would become self-reproducing and viable long term.

For the propagation efforts, the MCT used three sites for collecting gravid (egg release condition) females and glochidia (mussel parasitic life stage): Lower St. Croix River at Hudson, Wisconsin; Pool 11 at Cassville, Wisconsin; and Pool 14 at Cordova, Illinois. These sites were chosen for their Higgins eye pearlymussel genetic variability and availability of individuals.

In the summer of 2001, this relocation was accomplished as part of a mussel workshop conducted by the Illinois Chapter of the American Fisheries Society. As part of the collection of gravid Higgins eye pearlymussels, the group hand-rubbed off any zebra mussels attached to the mussels prior to relocation. Additional processing techniques were used prior to laboratory and relocation activities.

Any unused Higgins eye pearlymussels were placed in two specific stockpile sites within the Cordova bed for future propagation efforts. Prior to placement at the stockpile sites, “cleaning” zebra mussels off the live mussels became a common practice. As with any relocation site, the stockpile sites diminshes over time based on escape, burrowing and natural mortality.

Since 2002, the multiagency and academic groups have come together for a one-day mussel collection effort to restock the stockpile sites using shallow water dwelling mussels. These mussels are easily accessed by non-diving surveyors with limited experience using their hands and feet to discover mussels. Every mussel is identified, cleaned of any zebra mussels and returned to the water. All Higgins eye pearlymussels are returned to the stockpile sites for future propagation needs and all zebra mussels are destroyed and disposed of properly.

Since propagation efforts have concluded for the most part, the annual cleaning effort has evolved into a one-day mussel event getting agency folks together in an educational, team-building exercise. The annual Cordova Mussel Cleaning is held on the first Wednesday of August. Upwards of 75 people usually attend. The group generally collects several thousand mussels representing more than 25 live species.

-30-

• Date Taken: 09.15.2021
• Date Posted: 09.15.2021 11:12
• Story ID: 405299
• Location: ST. PAUL, MN, US