Reassessment of Freshwater Unionid Mussel Diversity and Abundance in the Walnut River Basin, Kansas

Species diversity of unionid mussels of the Walnut River Basin, Kansas was reassessed in 2017 and compared with surveys from 1979 and 2001. Our 1979 study surveyed 120 sites in the basin collecting 18 extant species. We resampled 87 of these sites in 2001, finding evidence of 8 extant species. In 2017 our survey of four sites collected 5 extant species. The most abundant species were Amblema plicata in 1979, A. plicata and Quadrula quadrula in 2001, and Quadrula pustulosa in 2017. The most abundant bivalve mollusk in 2017, comprising 36% of live mussels, was Tritogonia verrucosa. The non-unionid species Corbicula fluminea was absent from sample sites in the basin in 1979, comprised 51% of live individuals in 2001, and 24% of live individuals in 2017. Non-native Zebra mussels (Dreissena polymorpha) were found in the basin in 2017, but not in the earlier surveys. These results demonstrate that changes in mussel abundance and diversity have occurred since the 1979 survey, but do not suggest continual dramatic declines in mussels in the Walnut River Basin.