Invertebrates on cut weed removed during weed‐cutting operations along an English river, the River Frome, Dorset

摘要

Abstract.During weed‐cutting operations on the River Frome, Dorset, England, cut weed (800t), together with associated macroinvertebrates, was removed at five boom sites down the river. The mean density of macroinvertebrates removed was 30 individuals per g dry weight of cut weed which was equivalent to 6mg dry weight per g of cut weed, ca. 4900 individuals per square metre of river bed, or 0.9g dry wt/m2of river bed.The cut weed removed was populated chiefly by larvae of Chironomidae and Simuliidae although the numbers and biomass ofEphemerella ignitaPoda andBrachycentrus subnubilusCurtis were a significant part of the total macroinvertebrate population.Macroinvertebrates removed on cut weed were estimated as ca. 20 by number and ca. 12 by biomass of the total population from published values. The river (50km) was difficult to sample immediately prior to weed cutting because of rapid changes in the density and position of invertebrate populations, the immense sampling effort required and the non‐synchronous system of cutt