QUALITATIVE VERSUS QUANTITATIVE SAMPLING TO EVALUATE POPULATION AND COMMUNITY CHARACTERISTICS AT A LARGE-RIVER MUSSEL BED

Quantitative and qualitative sampling methods were used to study commu nity characteristics, density, recruitment rates and population demogr aphy of abundant species of freshwater mussels (Family: Unionidae), at Ohio River Miles 444.2-445.6 in July 1989 and September 1990. Mean un ionid densities (+/-SD) based on 100, 0.25-sq m total substratum sampl es at four sites ranged from 4.4 +/- 6.8 to 52.4 +/- 13.9 individuals/ sq m. Mean densities of Corbicula fluminea ranged from 66.8 +/- 67.7 t o 1352.8 +/- 96.1 individuals/sq m. Shannon-Weaver species diversity l og2.306 (2.32 to 2.50) and evenness (0.76 to 0.90) at these sites indi cated an equitable distribution of species within the community. Indiv iduals of two abundant species, Quadrula pustulosa pustulosa and Pleur obema cordatum, were represented by most size classes, indicating gene rally sustained recruitment with some annual variation. Both sampling methods provided similar estimates of community composition, species r ichness, diversity and evenness. A comparison of these results with th ose from a previous survey at this bed indicates no major changes in b iotic conditions between 1984 and 1989-1990.