A QUANTITATIVE SURVEY OF THE UNIONID MUSSEL COMMUNITIES BELOW FOUR DAMS ON THREE WISCONSIN TRIBUTARIES OF THE ST. CROIX RIVER

Matthew S. Berg, Joshua J. Watt, Lenora Benge Briiggs, Andrea N. Edling, Jade L. Johson, Joshua J. Larsen, and Jonathan R. Wick, Grantsburg High School

During the summer of 2005, students from Grantsburg High School and their instructor quantitatively analyzed the mussel communities below four dams on the Yellow, Clam and Wood Rivers in northwestern Wisconsin. An additional high density site on the Yellow River was sampled as a comparison control. At each site, mussels and substrate were collected from 100 quadrats (0.25m2). Substrate was separated into five size classes and weighed, and all mussels were identified, measured and aged using annular rings. A numbered vinyl tag was attached to the first 200 mussels at each site for future growth analysis. The Wood River below the Memory Lake Dam had the highest diversity with 20 species while the Yellow River below the Spooner Dam had the lowest diversity with only 6 species. The highest densities occurred at the control site on the Yellow River with 27.5 mussels/m2, and on the Clam River at the Clam Lakes Dam with 26.9 mussels/m2 and the Clam Falls Dam with 19.0 mussels/m2. The Memory Lake Dam site had the lowest density with only 9.2 mussels/m2. The oldest mussel community occurred at the Yellow River control site with a mean of 17.3 annular rings/mussel while the youngest site was the Memory Lake Dam site with a mean of 8.2 annular rings/mussel.