Effects of surface runoffs on the species diversity and abundance of the fishes of Ibiekuma Stream, Ekpoma, Edo State, Nigeria

Abstract

This study examined the effects of surface runoffs on the fish abundance, diversity and distribution, at three selected stations of Ibiekuma stream, Ekpoma, Nigeriabetween July and December 2003. The physico-chemical properties of the water were also monitored  during the period. The results showed that the water chemistry, the fish species diversity and distribution were different among the stations. The species diversity and abundance as well as the condition factor of the fishes were significantly lower at Station 2, which received surface runoffs impact, than at Stations 1 and 3. It was also shown that the fishes at Station 2, fed mainly on nematodes and Chironomid larvae and pupae, which are known bio-indicators of organic pollution. The observation of improved water chemistry, fish species diversity and abundance at Station 3, which is downstream of the runoffs-receiving Station 2, showed the temporary and non-residual nature of the pollution and indicated organic pollution from surface runoffs. The ability of the stream to purify itself after pollution was demonstrated. It was also demonstrated that apart from diversity indices and water quality parameters, food and feeding habits of fish could be used in assessing organic pollution impacts.