A closeup of two juvenile winged mapleleaf mussels on a "silo" in which they were placed in the Mississippi River at St. Paul, Minnesota. USFWS photo by Phil Delphey.

Five juvenile winged mapleleaf on a silo they will inhabit in the Mississippi River at St. Paul, Minnesota. They will be placed in the river when they grow to 5-6 centimeters. USFWS photo Phil Delphey.

On July 3, 2008 a potentially historic event occurred quietly on the Mississippi River in St. Paul, Minnesota, less than a mile from the Service's regional office at Ft. Snelling.  Biologists from the Service's Twin Cities Field Office and the National Park Service placed 10 juvenile winged mapleleafs, a federally endangered freshwater mussel, into small growth chambers called silos, which were then placed into the river.  As far as we know, this is the first time that the winged mapleleaf has been in the Mississippi River since it was extirpated there, probably decades ago.  The Mississippi River is one of about 34 rivers from which the winged mapleleaf has been extirpated.  It currently occurs in five rivers, with strong populations confirmed only in the St. Croix River in Wisconsin and Minnesota and in the Saline River in Arkansas.

The winged mapleleaf will likely be kept in the growth chambers until they are 5-6 cm in length to reduce their vulnerability to predation.  In the first 26 days in the silo, the mussels grew about 1.6 mm.  At that rate of growth, they may not be ready for release for about two years.  Nevertheless, this is a significant step towards the Service's objective of establishing populations of the species in at least five rivers within its historical range. 

The winged mapleleaf propagation effort is a cooperative project among the Service's Twin Cities Ecological Services Field Office and Genoa National Fish Hatchery, the St. Croix National Scenic Riverway, the Departments of Natural Resources of the States of Wisconsin and Minnesota, University of Minnesota, the U.S. Army Corps of Engineers, and Macalester College.