Freshwater mussels live on the bottom of our rivers and strain suspended bacteria, algae and organic detritus from the water by sucking it into their siphons--they're like Mother Nature's wastewater treatment plants. Since the river channel moves around with changes in water level, they don't attach to the bottom like mussels that live along the ocean shore, but instead use their foot to move around as conditions make it necessary.
Kansas has a rich species diversity, with 48 species originally known from the state. Unfortunately, due to stream siltation, habitat degradation, and dewatering many of our mussel species are in real trouble. Mussels depend on other organisms as hosts for their larvae, and several mussel species are in trouble because of declines in the host fish needed by their larvae. There are currently 10 species listed on the Kansas state list of Threatened and Endangered Species, and another 11 on the Kansas list of Species In Need of Conservation.
Source: Angelo, R.T., M.S. Cringan, E. Hays, C.A. Goodrich, E.J. Miller, M.A. VanScoyoc and B.R. Simmons. 2009. Historical changes in the occurrence and distribution of freshwater mussels in Kansas. Great Plains Research 19:89-126.