Fish species diversity as indicator of pollution in Ikpoba River, Benin City, Nigeria

The composition and distribution of fish in the Ikpoba reservoir were investigated. A total of fifty-seven species of fish belonging to thirty-nine genera and twenty-three families were recorded. Of these, 46 species were recorded at the upstream station, 35 at the reservoir, 24 at the slope and 32 at the downstream station. The percentage compositions were 81%, 61%, 42% and 56% respectively. There were 21 ubiquitous species while the distribution of the other species showed variability indicating effects of habitat condition. Species diversity indices showed that the upstream section was richer, more diverse with species more evenly distributed than the other stations. Heavy metal analysis of the dominant fish species showed higher mean levels than the background levels. Metal contamination factor and bioaccumulation quotient were variable in the fishes and in the stations but followed a ranked order of 3 > 2 > 4 > 1 by station. Comparison of stations using ANOVA revealed a significant difference (P < 0.05) between the upstream and the slope stations.