author(s)
Anupama Saha, Susmita Gupta

abstract
Aquatic insects comprise taxonomically diverse and ecologically important and interesting group of animals in fresh water systems. Among them the aquatic and semi-aquatic Hemiptera occupies an important position. Over the Cachar plain the River Barak has an extremely meandering course forming large number of oxbow lakes locally known as anua. For the present study Gandhinagar anua, Bekirpar anua and Shibnarayanpur anua were selected from the district. Insects were collected seasonally by standard methods from all the possible substrata during 2012-13. The study recorded 8 families of both infra-orders Nepomorpha and Gerromorpha. Nepomorpha families were higher in number which included Corixidae, Nepidae, Notonectidae, Pleidae and Belostomatidae while family Gerridae, Veliidae and Mesoveliidae were recorded from Gerromorpha. Various biomonitoring scoring indices like BMWPTHAI, ASPTTHAI and NLBI were used to assess the ecosystem health of the oxbow lakes. This study finds that Gandhinagar anua is in relatively better condition, but also requires attention as human activity determines the fate of an ecosystem.