Abstract:
The water quality and crustacean zooplankton of Utor River, a relatively pristine freshwater body in
Edo State, Nigeria was investigated at four stations. The Utor River is slightly acidic, well
oxygenated, oligotrophic and low in solids, conductivity, cations and heavy metals. A total of 380
individuals comprising eleven taxa were recorded, and the highest density was observed at Station 1
(29.9%) followed by Stations 2 (25.0%), while Stations 3 and 4 accounted for 24.2% and 21.1%
respectively. Overall density showed no significant difference (P> 0.05). Copepoda represented by the
family Cyclopoidae contributed 57.89% of the total density. The dominant species were
Cryptocyclops bicolor, Ectocyclops phaleratus and Mesocyclops ogunnus. The Harpacticoida (15% of
the population) was represented by one taxon Bryocamptus birsteini which was well represented in all
the stations. The water quality assessment shows that the river is still relatively pristine and
unperturbed. The crustacean zooplankton assemblage was cosmopolitan and dominated by the
Copepoda in terms of the number of species and overall abundance, with Crypptocyclops bicolor as
the most important species. The overall abundance and diversity of zooplankton was relatively low
