Interactive effects of near-bed flow and substratum texture on the microdistribution of lotic macroinvertebrates

Abstract

The interactive effects of substratum texture and near-bed velocity on the small scale spatial distribution of lotic macroinvertebrates was investigated in laboratory flumes with variations in flow among microhabitat patches (-0.015 to 0.035 m2). There were three different substratum textures, coarse, intermediate and smooth, and three species with contrasting velocity preferences, Gammarus pulex, Oreodytes sanmarkii and Baetis rhodani. The number of individuals retained in the flumes was highest for B. rhodani and O. sanmarkii on the rough substratum, but maximum numbers of G. pulex occurred on the intermediate substratum texture. Microdistribution patterns with respect to near-bed flow dif..