FRESH-WATER MUSSELS (BIVALVIA, UNIONIDAE) IN THE VERDIGRIS, NEOSHO, AND SPRING RIVER BASINS OF KANSAS AND MISSOURI, WITH EMPHASIS ON SPECIES OF CONCERN

We examined freshwater mussel assemblages at 99 sites from 1993 to 199 5 in the Arkansas River system of southeastern Kansas and southwestern Missouri. Emphasis was placed on assessing the distribution, relative abundance, and habitat use of five unionid candidates for future fede ral listing (species of concern): Lampsilis rafinesqueana Frierson, 19 27, Ptychobranches occidentalis (Conrad, 1836), Cyprogenia aberti (Con rad, 1850), Quadrula cylindrica (Say, 1817), and Alasmidonta marginata Say, 1818. We collected a total of 15,068 mussels of 35 species, incl uding 1,301 L. rafinesqueana, 83 P. occidentalis, 29 C. aberti, seven Q. cylindrica, and one A. marginata. The three most abundant species c ollected from our study were Amblema plicata (Say, 1817), e. metanevra (Rafinesque, 1820), and e. pustulosa (Lea, 1831). However, species ab undance rankings varied from stream to stream; for example, L. rafines queana was the most abundant species collected in the Spring River. Ha bitat use by candidate species varied considerably between streams, ho wever, they were consistently found in shallow riffles and runs (mean depths 25.0-33.7 cm), with stable and moderately compacted substratum, predominantly gravel, with a minimum of silt.