OLIGOTROPHIC ASSESSMENTS OF OGUN COASTER WATER USING PHYSICAL, CHEMICAL AND BIOLOGICAL INDICES

Abstract

In recent times, various efforts have been documented to mitigate water pollution, therefore using physical, chemical and biological indices needs to be encouraged. The research aimed to assess water quality, length- weight relationship, composition and abundance in fish species of Ogun coastal water, Southwest, Nigeria which is known for industrial and agricultural activities be screened for human safety. Water and fish species were obtained following standard procedures, some physico-chemical analyses of the water were examined in-situ while others were measured ex-situ. Metals in the water and fish species were determined using Atomic Absorption Spectrophotometer. Data obtained were analyzed using SPSS, mean values were compared using ANOVA, post- hoc test using Student-Newman-Keuls and P<0.05 was considered to be statistically significant. Length-weight relationship, condition factor, species richness, total abundance, Simpson index, Shannon Weiner index, species evenness, dominance, Margalef species richness and Fisher alpha were calculated. Fish diversity indices were calculated using PAST software, while, the fish species richness was estimated. Result obtained showed significant changes in the water physico-chemical parameters and heavy metals in water and fish organs of the different species. Fifteen fish species indentified with Pelmatolapia marie having the highest abundance (132,406 individuals), Heterobranchus bidorsalis, Clarias anguillaris and Schilbe intermedius had the lowest abundance with 1, 3 and 7 individuals respectively. The fish diversity was moderately even, but showed negative allometric growth. Decline in the fish species might be connected to the habitat degradation in Ogun coastal water which needs to be constantly monitored for effective fishery and stock management.