1. U.S. Geological Survey, Biological Resources Division, Great Lakes Science Center, 1451 Green Road, Ann Arbor, Michigan 48105, U.S. Geological Survey, Biological Resources Division, Upper Mississippi Science Center, 2630 Fanta Reed Road, LaCrosse, Wisconsin 54603, and U.S. Fish and Wildlife Service, Green Bay Fishery Resources Office, 1015 Challenger Court, Green Bay, Wisconsin 54311