Author(s): Adadu MO, S Omeji and AA Garba

Abstract: The study was done to investigate the seasonal diversity and abundance of zooplankton community index of River Okpokwu. In dry season, a total number of 1219 zooplankton whereas in rainy season, a total number of 611 zooplankton belonging to four classes; viz Copepoda, Monogononta, Branchiopoda and Class Insecta was encountered during the study period. Three species of Class Copepoda (Mesocyclops sp, Diaptomus sp and Bryocamptus minute), four species of Class Monogononta (Trichocerca sp, Branchionus falcatus, Branchionus angularis and Polyarthra sp), three species of Class Branchiopoda (Chydorus sp, Bosmina sp and Diaphnia puplex) and four species of Class Insecta (Chironomid sp, Gerris remigis, Gyrinus sp and Corixid sp) were encountered. In terms of zooplankton diversity index, Shannon Weinner diversity index (4.57, 4.51 and 4.56) were recorded for stations A, B and C, respectively in dry season but 4.47, 4.45 and 4.49 in stations A, B and C were recorded in rainy season while Margalef Index (4.43, 4.21 and 4.41) were recorded in stations A, B and C in the dry season, and 4.22, 3.99 and 4.27 were recorded in rainy season for stations A, B and C, respectively. Correlation occurred between physicochemical parameter and the zooplankton. In conclusion, River Okpokwu is highly rich in taxa and dominance of zooplankton in dry season. Among the zooplankton, Rotifers of genus Brachionus were most abundant. Therefore, River Okpokwu is a rich ecological ecosystem with high plankton diversity that can sustain fishery development.

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