Winged Mapleleaf Recovery
Releasing Captive-Reared Mussels into the Mississippi
State and federal biologists released captive-bred winged mapleleaf into the Mississippi River, after an absence in the River of over 100 years.
Photo by USFWS
Great things usually start out small. Culminating a morning on the river that included a somewhat coincidental encounter with the Secretary of the Interior and the Governor of Minnesota, a group of state and federal biologists released federally endangered winged mapleleaf mussels into the Mississippi River on August 17. Winged mapleleaf were once broadly distributed throughout the central United States and inhabited much of the Upper Mississippi River. Before the recent release, they were absent from the River for about 100 years.
The reintroduction of winged mapleleaf took place in the heart of the Minneapolis/St. Paul metro area – in a reach of the Mississippi River that has changed markedly from early in the twentieth century when sewage and industrial pollution rendered it unsuitable for all but the most tolerant of aquatic species. The river now boasts good water quality, excellent substrate, and a trophy fishery. Zebra mussels – the bane of once magnificent mussel beds further downstream – are sparse in this reach, just below Upper Mississippi River Lock and Dam 1.
Although limited in extent and subject to threats of its own, this reach of the Mississippi River is becoming one of the most important areas for mussels in the Upper Midwest. In addition to winged mapleleaf, the Service’s Genoa National Fish Hatchery has worked as part of the Mussel Coordination Team to propagate and release thousands of Higgins eye, another endangered species into this reach. Zebra mussels had devastated population of Higgins eye in downstream reaches of the river and continue to pose a major threat. Minnesota Department of Natural Resources has also released hundreds of snuffbox here, another federally endangered species. These and the numerous other native mussel species that are becoming reestablished in this reach of the Mississippi are threatened by expanding populations of zebra mussels in lakes upstream in the watershed. In addition, the sediment-laden Minnesota River enters the Mississippi just downstream of the high-quality reach.
Winged mapleleaf is a short-term brooder and challenging to propagate – only nine individuals had survived and reached the size at which they could be safely released this summer. Cages in the St. Croix River may hold additional winged mapleleaf that are still too small to release.
Biologists will return to the site where winged mapleleaf were released to monitor their growth and survival. Although the release on August 17 was noteworthy, thousands of additional winged mapleleaf may have to be released to have a reasonable chance of reestablishing a viable population. In September, biologists on the team will begin searching the St. Croix River, on the boundary between Minnesota and Wisconsin, for females that are brooding glochidia (larvae) that are ready to be released onto host fish. These females will be taken to Genoa National Fish Hatchery where mussel propagation biologist, Nathan Eckert, will use their glochidia to infest channel catfish. The catfish will overwinter at the hatchery before being released into cages on the St. Croix River to begin a new cohort and to continue to work towards the recovery of the species.
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