Date of this Version
A survey of 96 locales in the Big Blue River and its minor tributaries supplemented by museum vouchers documented the presence or former presence of 25 native unionid mollusk species and one introduced bivalve. Including the previously reported Little Blue Basin, the total documented unionid inventory ofthe Big Blue Basin consists of twenty-six species. Over a third of these species may have been extirpated from the basin, and many of the surviving species appear to have experienced significant range reductions. Habitat in the region is adversely impacted by surface and subsurface water withdrawals, erosion/siltation, and grazing. Chemicals and other pollutants from agricultural fields probably exert a further deleterious impact upon the fauna of the region. Despite these conditions, the Big Blue Basin continues to provide habitat for a number of species that are generally uncommon in northern Kansas and Nebraska.