Godwin Asibor and Funso Adeniyi

The zooplankton of Asejire reservoir was identified and its community structure assessed between April 2017 and March 2018 in nine selected sites. Three stations each were established along the horizontal axis of the reservoir, covering the riverine, transition and lacustrine zones of the lake. The taxa richness, diversity, and evenness indices were calculated using Shannon-Wiener, Simpson and Margalef indices. A total of 146 species of zooplankton was recorded comprising Rotifera (80), Copepoda (24), Cladocera (22), Protozoa (7), Ostracoda (7) and Insecta larvae (6). Notholca foliacea, Brachionus angularis, B. budapestinensis, B. calyciflorus, B. caudatus, B. cochlearis, B. dimiatiatus, B. patulus and Bosminia longirostris were recorded in all the stations while 17% of the occurring species were recorded only at one stations each. Rotifers accounted for over 50% of the total occurrence, followed by the Cladocera (17%) and Copepoda (16%). The Protozoan were the least occurring species with 2%, followed by Ostracoda (4.63%) and Insecta (3.96%). The riverine zone had the highest occurrence of zooplankton species, whereas the lacustrine zone had the lowest occurrence. The presence of some pollution indicator species is a cause of concern and there is the need to ensure holistic and effective monitoring measure to safeguard the reservoir from further anthropogenic intrusion from the receiving rivers and streams.

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