Spatial and seasonal distribution of macrobenthic fauna ofthree rivers of Manipur

Abstract

Benthic fauna of three important rivers of Manipur state viz., Khuga, Thoubal and Imphal were studied during 1999 - 2000.Macroinvertebrate zoobenthos population was low in all the rivers and was found between 85-1,255 µm-2. In Khuga (129-1,255 µm-2) and Thoubal (173-1,100 µm-2 ) rivers macroinvertebrate benthos population were poor to medium where as inthe Imphal River all the three stretches studied showed lowered macroinvertebrate population (85-390 µm-2). During pre-monsoon period there was maximum benthos density in both the stretches in Thoubal, Khuga and Imphal rivers, whereas inthe middle stretches of Imphal River, maximum population was observed in post-monsoon. Upper stretch showed richerbenthos population both in terms of density and species composition in Khuga and Thoubal rivers. In the Imphal Riverdistinct spatial variation of macroinvertebrate benthos population was lacking, but species composition was richer in lowerstretch. Altogether nine macrozoobenthic groups were observed during the study and the details are presented in this paper.