Abstract: Cladocerans and Copepods are microcrustacean present in fresh and marine water bodies. Occurrence of these microcrustaceans revealed a strong dependence of development on discharge pattern.  Population density and seasonal variations of microcrustaceans were extensively studied on Sikrahna river running across Bagaha. Cladocerans & Copepods form a major group of herbivores mesozooplankton. In the present study, ecophysiological knowledge about between difference in metabolic and reproductive rates, feeding, selectivity and element composition were compiled. A total no. of 5 species of Cladocerans and 3 species of copepods were collected from Sikrahna river during study from July 2010 to June 2011.

Keywords: Cladocerans, Variation, density, dominant, Microcrustaceans, mesozooplankton.

| DOI: 10.17148/IARJSET.2020.71015