Each fall, hatchery biologists working with U.S. Park Service staff, MN DNR mussel biologists and staff from other U.S. Fish and Wildlife Service offices visit the St. Croix as many as 15 times looking for the federally endangered Winged Mapleleaf that thrive in the clean, clear water. Females holding mussel larvae are brought back to Genoa National Fish Hatchery, the larvae (glochidia) are allowed to attach to channel catfish and then the female mussels are returned to the St. Croix River. In the wild the larval mussels remain attached to the catfish until late spring when the water begins. In late May 2023 juvenile Winged Mapleleaf began to drop off at the Upper Midwest Environmental Sciences Center after they’d overwintered on channel catfish in their ponds. Some juveniles went into laboratory culture, while others were stocked into the Chippewa River. Around 3,000 0.3 mm juveniles were stocked in two events at a site where adult Winged Mapleleaf were reintroduced in 2016, and Higgins Eye were stocked in 2017. A quantitative survey of the site in 2021 showed that both species have survived and grown well alongside a large population of federally endangered Sheepnose. We hope that even a few of these Winged Mapleleaf juveniles will survive to adulthood and contribute to the genetic diversity of this reintroduced population.
By Megan Bradley

Photo: Biologists stock WML juveniles on the Chippewa River into a tube to allow them to settle in the mussel bed. Photo credit: USFWS.