Figure 1. Winged mapleleaf valves collected during upper river survey.
 
 

Second collection of winged mapleleaf valves from the upper St. Croix River

Mark C. Hove¹, Daniel C. Allen, Russel S. Derhak, Kristin M. Swenson, Jana E. Thomas, and Daniel J. Hornbach

Macalester College, Biology Dept., 1600 Grand Avenue, Saint Paul, Minnesota 55105
¹ Hove@macalester.edu, 651.696.6827
 

The federally endangered winged mapleleaf has experienced a dramatic reduction in its range. Quadrula fragosa (Conrad 1835) at one time inhabited at least 34 river systems in 12 states (USFWS 1997). One of the last known reproducing populations occurs in the St. Croix River where the river forms the border between Minnesota and Wisconsin. St. Croix Falls, Wisconsin is the site of a hydropower dam on the river that prevents fish passage upstream. The hydropower plant has been in operation for nearly 100 years and there are differences in the fish and mussel fauna above and below the dam.

Until very recently winged mapleleaf were thought to occur only downstream of the St. Croix Falls dam. Doolittle conducted a mussel survey of the St. Croix and Namekagon rivers and found that Q. fragosa occupies a relatively small reach of the lower river (Doolittle 1988). Two years ago evidence arose suggesting the range of winged mapleleaf may extend upstream of the dam. In 1999 we worked with Lisie Kitchell, Wisconsin Dept. of Natural Resources, and were funded by both the U.S. Fish and Wildlife Service and the Minnesota Environmental and Natural Resources Trust Fund as recommended by the Legislative Commission on Minnesota Resources. We found three, weathered winged mapleleaf valves at Wild River State Park, Minnesota, approximately nine miles upstream of the dam (Hove et al. 1999).

This summer the National Park Service, St. Croix National Scenic Riverway supported survey work to better describe the range of winged mapleleaf in the St. Croix River. Nearly twenty sites have been surveyed above and below the St. Croix Falls dam to date. So far at least two winged mapleleaf valves (Figure 1) were collected relatively near to where the winged mapleleaf valves were collected in 1999. We will be working with the Wisconsin Dept. of Natural Resources and Minnesota Dept. of Natural Resources to conduct additional winged mapleleaf surveys this summer and fall. This winter we will send winged mapleleaf valves to several malacologists to confirm our identifications. Live winged mapleleaf have not been observed upstream of the St. Croix Falls dam. Additional work is needed to describe the range of winged mapleleaf in the St. Croix River and determine if the species is still extant upstream of the dam.

We thank Jill Medland, Bob Whaley, and Randy Ferrin who have provided wonderful administrative and logistic support for this project.

Literature Cited

Doolittle, T. C. J. 1988. Distribution and relative abundance of freshwater mussels in the Saint Croix National Scenic Riverway. Report to Cable Natural History Museum - Sigurd Olson Environmental Institute. Ashland, Wisconsin. 230 pp.

Hove, M. C., L. A. Cunningham, K. G. Esse, and D. J. Hornbach. 1999. Range extension of the federally endangered winged mapleleaf: valves collected from upper St. Croix River, Minnesota. Triannual Unionid Report 18: 9.

U.S. Fish and Wildlife Service. 1997. Winged mapleleaf mussel (Quadrula fragosa) recovery plan. Fort Snelling, Minnesota. 69 pp.