Macroinvertebrate drift patterns of two Thai streams

Abstract

From March to October, 1993, macroinvertebrate drift patterns in the disturbed stream in Ban Nong Hoi (BNH) and the relatively pristine stream in Doi Chang Kian (DCK), Chiang Mai, Thailand were compared.
Results show that day-night changes in drift were mainly controlled by light rather than water temperature. Maximum drift was recorded soon after dusk and night drift was generally higher than the day drift.
Baetidae, Chironomidae, Hydropsychidae and Lepidostomatidae accounted for high drift number at night while Simuliidae was found to be day-active.
Monthly invertebrate drift was primarily influenced by benthos density and flow regime of the streams. The highest drift was recorded in March which coincided with the highest population density of the benthos, and the lowest at the peak of the rainy season when the flow regime of the streams was very high.