Neil B. Ford Department of Biology University of Texas at Tyler Tyler, Texas Freshwater Mussels (Unionidae) of the Big Cypress Bayou in Northeast Texas

Most diverse fauna in U. S. Most imperiled group Over 300 known species more than 40% Dense multispecies bed Exceed other benthos biomass 10 to 100/square meter by 10 fold

over 50 species in the state eastern Texas mussel fauna differs from other drainages (27 recorded or possible in Big Cypress Bayou) Whether declining is unknown? very little research Texas Parks and Wildlife Department (TPWD) reports

harvested: pearls; shells used for various purposes water pollution Very sensitive to water quality 10 times more to nitrogen than minnows Agriculture, oil production, eutrophication introduced species Asian clam (Corbicula sp.) Competitor?

Biggest threat disturbance in water flow (Neck 1982) altered population structure and abundances altered substrate composition altered water quality block migratory host fish

Informal Sampling sites for sampling are chosen without a formal design chosen by substrate, presence of dead mussels on banks, current, etc. cannot assume these samples represent mussel population accurately this method works to detect the presence of species

Systematic Sampling type of cluster sampling selecting sampling units at equal intervals (random direction) provides good spatial coverage (sampling units widely distributed) some quadrats contain mussel beds, others do not

Mussels should be a useful fauna to examine to evaluate the effect of flow rates on the overall improvement of the aquatic ecosystems of these drainages.