Effect of drift sampler exposure time and net mesh size on invertebrate drift density in the Njoro River, Kenya

Abstract

Although invertebrate drift is an important ecological process in lotic ecosystems, very little is known about it in Kenyan rivers. The primary aim of this study was to investigate the effect of driftnet mesh size and exposure duration on drift density in 2017. Drift samples were dominated by Chironomidae, Baetidae, Simuliidae, Caenidae and Culicidae. The 100 μm mesh driftnet had the highest mean invertebrate density, followed by the 250 μm and 500 μm nets. Invertebrate drift densities decreased with increased exposure time. This study demonstrates that sampler mesh size and exposure time should be taken into account when characterising invertebrate drift in streams. Future studies should consider sampling different biotopes and during different seasons.

Keywords: lotic ecosystems, macroinvertebrates, Nakuru County, riffle habitats