Invertebrate drift and longitudinal transport processes in streams

Abstract

Benthic macroinvertebrates were disturbed from stream substrata and caught in drift nets at various distances downstream. Four experiments were carried out at several discharges in each of four streams with contrasting hydraulic transport characteristics. The numbers of all invertebrates and of Plecoptera in the water column at each distance were fit to a negative exponential function. The channel with the highest mean velocity had the lowest return rate (β). In any one channel, β decreased with increasing velocity; this relationship approximated a power function, with stream specific slope corresponding to channel hydraulics. The stream with a high fraction of dead zones had high β values t..