In an effort to transform winged mapleleaf glochidia into juveniles for release into the St. Croix River in an appropriate phenological manner that would increase chances for its survival, four glochidia-infested channel catfish were maintained by Mark Steingraeber, a fishery biologist at the La Crosse Fishery Resources Office, for a nine-month period (October 2003 - June 2004) at a thermal regime that closely followed the reported mean daily water temperature of the St. Croix River. All fish survived the winter and remained infested with glochidia while in cages that were submerged in a pond for five months. Fish were returned to individual aquaria during spring when mussel development resumed at water temperatures above 9°C. A total of about 3,500 active juvenile mussels were later recovered during a one-week period at the start of summer. An interagency team of divers from the U.S. Fish and Wildlife Service, National Park Service and Minnesota Department of Natural Resources subsequently assembled on July 2 near Marine-on-St. Croix, Minn., to place about 3,100 of the recently transformed juvenile winged mapleleaf mussels inside protective enclosures in the St. Croix River. It is hoped that many of these juvenile mussels will survive and continue to grow here, thermally 'in-synch' with their natural environment. The knowledge and experience gained during this successful long-term scientific investigation will soon be put to practical use by the Service and its partners with appropriate phenological propagtion efforts to help restore the St. Croix winged mapleleaf population and recover this species in other portions of its historic range.