Effects of lowhead dams on aquatic gastropods.

Impoundments dramatically affect both the physical and chemical conditions of rivers by converting free-flowing habitats to more lake-like conditions, changing flow regimes, altering water quality of streams (e.g., changes in temperature, reductions in oxygen), and increasing siltation upstream from the dam while increasing erosion downstream from the dam. These habitat alterations cause changes in aquatic faunas (e.g., fishes, freshwater mussels, and aquatic insects) by restricting distributions, isolating populations, reducing the numbers of native species, and increasing the numbers of non-native species. Several studies have documented effects of dams on fish, freshwater mussel, and aquatic insect communities, but few have addressed effects of dams on aquatic gastropods. The Conchologists of America (COA) provided funds to help me complete a study that addressed this issue. Data on how lowhead dams affect freshwater mussels are important for the protection of this imperiled fauna.