Turkish Journal of Fisheries and Aquatic Sciences
2009, Vol 9, Num, 1 (Pages: 01-08)
Influence of Watershed Activities on the Water Quality and Fish Assemblages of a Tropical African Reservoir
Moshood Keke Mustapha 1
1 University of Ilorin, Department of Zoology, PMB 1515 Ilorin, Nigeria
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Agricultural and fisheries activities around the watershed of an African tropical reservoir (Oyun Reservoir, Offa,
Nigeria) were found to have contributed significantly to the eutrophication of the reservoir. This is evident from the high
amount of nitrate (6.4 mg/L), phosphate (2.2 mg/L) and sulphate (16.9 mg/L) in the water body. These nutrients came from
fertilizer run-offs from nearby farmlands and were found in higher concentrations in the rainy season, which was usually the
peak of agricultural activities in the locality. The eutrophication altered the food web cycle with the bloom of filamentous
algae and the decline in zooplankton population. The effect of this scenario affected the fish species composition and
abundance with the dominance of cichlids (planktivorous group) in the fish population. Best management practices (BMP) to
control and reduce the eutrophication and improve the fish assemblages should be adopted and adapted to suit the situation in
the reservoir.
Keywords :
eutrophication, nitrate, phosphate, cichlids, management