Invertebrate Drift in a Central Wisconsin Brook Trout Stream

Abstract

As part of a study evaluating the effects of removal of woody streamside vegetation on trout streams, monthly drift samples were collected in the Little Plover River during 1972 to determine taxa, density, and seasonal changes in numbers of invertebrates in an upstream meadow and two downstream brushy areas. Results of this drift investigation favorably support the proposal of brush removal as a technique for managing small trout streams. Differences in drift between the meadow and successive downstream brushy stations were: mean annual density of drifting organisms decreased from 614 to 273 to 130 organisms/100 m3; drift biomass was highest in August and decreased downstream from 4.00 to 1.34 to 0.07 g/100 m3 (wet weight); and the mean annual density of drifting detritus decreased from 34.2 to 20.4 to 13.7 g/100 m3 (dry weight). Monthly mean density of detritus was positively correlated with monthly mean density of invertebrates, with r = 0.824.