Braven B. Beaty and Richard J. Neves, Virginia Cooperative Fish and Wildlife Research Unit, Virginia Tech, Blacksburg, VA 24061

Abstract. Rainbow mussels (Villosa iris) and Asian clams (Corbicula fluminea) were deployed in cages at eight sites within the Clinch River watershed, VA to determine differences in responses of six physiological parameters. Mussels and clams were collected at a site in Little River, Russell County, VA and were moved to cages at five sites in the Clinch River, and one site each in Copper Creek, Stock Creek, and Little River. After 30 days, animals were removed from the cages, sacrificed, dissected, and the tissues frozen. Glycogen content, RNA:DNA ratio, and activities of acetylcholinesterase, phosphofructokinase, fructose-1,6-bisphosphatase, and cellulolytic enzymes were measured on various tissue fractions from each species. The experiment was performed in fall (September-October), spring (May-June), and summer (July-August). Differences (p<0.05) were found among sites for all six parameters, as well as among seasons and between species. Patterns of variation among sites were different for the two species. Using Asian clams as surrogates for unionids must be verified as valid for each field monitoring case.