Native mussels with zebra mussels attached that were collect from the St. Clair River Delta - Photo by James Boase

Tony Brady collects native mussels from the Black River, Michigan, a tributary of the St. Clair River - Photo by James Boase

Biologists from Michigan Department of Natural Resources (MDNR), Walpole Island First Nation (WIFN), USGS Great Lakes Science Center (GLSC), DTE Energy, Genoa National Fish Hatchery (GNFH), and Alpena FRO met, on September 1, at the Walpole Island Heritage Center. 

The purpose was to bring together biologists that have been working on Great Lakes mussel issues especially those affecting the Huron Erie Corridor (HEC) and to provide a forum to discuss recent findings and provide direction for future rehabilitation efforts. 

Resource managers from WIFN have been leading the efforts in establishing refuge areas within the St. Clair River Delta with the focus of maintaining and protecting the remaining native mussel populations on the Delta. 

The research leading up to the establishment of the refuge areas was largely a part of the cooperation between WIFN, Environment Canada, GLSC, and DTE Energy.  More recently the USFWS and Michigan DNR have joined in on these efforts.

At the meeting Mussel Biologist Tony Brady from the Genoa NFH presented recent innovative propagation techniques that have been successfully used in supplemental stocking or the reintroduction of federally listed mussels back into tributaries of the Mississippi River. 

Similar to the populations on the Mississippi River System, the populations on the St. Clair Delta have been declining or have been extirpated from many areas due to the negative effects of the exotic zebra mussel.  Since the introduction of the exotic zebra mussel in the 1980’s, native mussels have been steadily declining or have been eliminated from most areas of the Great Lakes. 

Although zebra mussels do not directly parasitize native mussels they do attach themselves in large numbers to the shells of the native mussels, preventing the mussels from foraging, reproducing and dispersing their progeny. 

Historical research indicates that the highest densities and greatest diversity of native mussels were found in deeper locations in Lake St. Clair while shallow bays located in areas such as the St. Clair River Delta were considered marginal habitat.  Today only the areas that were once considered marginal habitat have a surviving population of native mussels.

The St. Clair River Delta is the largest delta system in the Great Lakes forming an international border between the United States and Canada.  The St. Clair River splits into three main channels along with multiple smaller channels as it moves through the delta.  On the U.S. side the delta has been intensively managed and altered with both residential and commercial use dominating most upland areas.  Steel sheet pilings separate most of the interface areas between upland areas and the river.  Canals have been dredged connecting once isolated bays to most channels.

In Canadian waters, WIFN has maintained most of the natural integrity of the delta.  Most channels have native emergent plant species which slow the flow of water into them or act as buffers separating upland areas from the river.  Numerous isolated bays having a limited access point from the river or from Lake St. Clair are still intact and have not been breached by man-made channels.  Travel within the shallow water bays is restricted and is not impacted by heavy recreational boat traffic unlike most location on the U.S. side of the delta.

The differences in land use practices between the U.S. and Canadian waters of the delta may help partially explain why preliminary results indicate that native mussels are doing better in Canadian than in U.S. waters.  Low boat traffic in isolated shallow bays results in less mussels being damaged by props or being dislodged.  Bays that have not been breached by canals do not receive a continuous introduction of new zebra mussels, and as a result native mussels have few attached zebra mussels.  In general most of the bays sampled on Walpole Island were relatively deeper than what was found on the U.S. side.