ABSTRACT
This study investigated the species composition and distribution of zooplankton of the River Siluko, Edo State, Nigeria, at four designated stations of the River from October, 2016 through January, 2017. Among the physical and chemical parameters studied, water level, flow rate, biological oxygen demand (BOD) and chemical oxygen demand (COD) showed significant difference (P<0.05), while the others were not significantly different (P>0.05). A total of 19 taxa comprising 185 individuals were encountered in the study. Of these, 11, 10, 13 and 17 taxa were recorded in station 1, 2, 3 and 4 respectively, while the number of individuals was 26, 40, 59 and 60 respectively. The overall abundance of the species collected was significantly lower in station 1(P<0.05) than in station 2, 3 and 4 which were so not different from each other. Percentage abundance of the taxa was 31.58% each for cladocerans and rotifers and 36.84% for copepods. Copepods accounted for s63.78%, cladocerans 27.56% and rotifers 8.66% of the total number of individuals. The order of decreasing dominance is copepods>cladocera>rotifers. Among the cladocerans, the family Macrothricidae was dominant in all the stations. Cyclopoid copepod dominated among the copepods as they were the only copepod family encountered, while among the rotifers, the family Brachionidae was dominant. Evenness index showed that station 2 had the maximum evenness and station 3 had the minimum. General diversity and species richness (d) was highest in station 4 and lowest in station 2. In all the stations, cyclopoid copepods were dominant followed by the cladocerans. The presence of aquatic macrophytes and the physico-chemical parameters influence the distribution and abundance of zooplankton in the study stations.
