Fish fauna of Oyun Reservoir, Offa, Nigeria

Abstract

Fish species composition, diversity and abundance of Oyun Reservoir, Otta, Nigeria, (a shallow tropical African Reservoir) was assessed monthly for two years between January 2002 - December 2003. The influence of the physico-chemical properties of the reservoir on the fish assemblages was also investigated. These with a view to increase production, identify threatened species and managing the fisheries for maximal sustainable exploitation. A total of 7713 fishes belonging to 9 families, 15 Genera and 18 species were collected using gill nets, cast nets and traps. The numerical abundance showed Cichlidae to dominate the families constituting 64.5% of the population with Tilapia zillii being the most abundant species (30.0%). Osteoglossidae and Heterotis niloticus were the least abundant family and species representing only 0.22% and 0.82% respectively in the fish population. Fish species were more abundant in the dry season than in the wet season, with Heterotis niloticus and Barbus occidentalis identified as threatened species in the reservoir, of which conservation efforts to prevent their extinction were recommended.

Key words: Physico-chemical factors; fish assemblage; conservation; reservoir; threatened species