U.S. Department of Defense


Date of this Version



Published by U.S. Army Engineer Waterways Experiment Station


Data from 24 grab samples, eight each taken with the Standard Ponar, Petite Ponar, and Shipek grabs from a backwater habitat were statistically compared using one-way analysis of variance. Total grabs produced 5696 organisms and 24 distinct taxa. Results showed no difference in catch efficiency among grab samplers for distinct taxa, total densities, and densities of the dominant taxa: Lirceus sp., Ilyodrilus templetoni, Hexagenia sp., Limnodrilus cervix, Limnodrilus hoffmeisteri, Sphaerium sp., and immature Ilyodrilus. The Petite Ponar grab captured significantly fewer immature Limnodrilus. This was attributed to clumped distribution of these worms rather than difference in gear type. Analysis of the cumulative percent composition of newly acquired species showed that second and additional replicates of each grab type accounted for 10 percent or less of the total standing crop, as also found by Ward (1976) in marine substrate types.