A COMPARISON OF 3 ARTIFICIAL SUBSTRATE SAMPLERS - MACROINVERTEBRATE DENSITIES, TAXA RICHNESS, AND EASE OF USE

Density, taxa richness, and composition of macroinvertebrates collecte d by three types of samplers were compared to determine their relative effectiveness for sampling in large rivers. Three multiplate samplers and three gravel basket samplers were deployed in the water column, a nd three large-cobble basket samplers were deployed on the river botto m. Two sites were sampled at monthly intervals from October 1988 to No vember 1989. Macroinvertebrate densities were significantly (p < 0.05) different among the three sampler types. Mean monthly macroinvertebra te density was highest on the multiplate samplers at both sites-1 742 and 1 239 macroinvertebrates/m2 and was lowest on the large-cobble bas ket samplers at both sites-174 and 266 macroinvertebrates/m2. Mean mon thly macroinvertebrate density was moderate on the gravel basket sampl ers at both sites-278 and 472 macroinvertebrates/m2. Mean monthly taxa richness was generally higher on the gravel basket and large-cobble b asket samplers than on the multiplate samplers. Multiplate samplers co llected larger numbers of Chironomidae, Oligochaeta, Trichoptera, and Ephemeroptera, but were least effective at collecting Turbellaria, bur rowing Ephemeroptera, Odonata, and Mollusca. Gravel basket samplers co llected larger numbers of Chironomidae, Oligochaeta, Crustacea, and Ep hemeroptera, and in addition collected more Odonata and Mollusca. Larg e-cobble basket samplers collected more burrowing Ephemeroptera.