Evaluation of Three Bottom Grab Samplers for Collecting river Benthos'

Author Institution: Environmental Monitoring and Support Laboratory, U.S. Environmental Protection AgencyThe performances of the standard Petersen, Ekman, and Ponar grabs were compared using 2 sets of samples collected from gravel, sand, silt, and mud substrates. The data obtained during this study show that estimates of macroinvertebrate populations may vary considerably depending on the grab utilized, the nature of the substrate, and the number of replicate samples collected. The Ekman sampler was rated as best in mud and also received a high rank in silt, while the Petersen received the highest rank only in sand. The Ponar sampler was the best overall grab on the basis of the numbers of individuals and taxa collected, precision, and mechanical operation