ABUNDANCE AND DISTRIBUTION OF SOME ECONOMICALLY IMPORTANT FISHES AT ERO AND EGBE WATER RESERVOIRS, EKITI STATE, NIGERIA

Abstract

The abundance and distribution of some commercially important fishes at Ero and Egbe reservoirs in Ekiti State, Nigeria was conducted between April 2014 and January, 2016. Four sampling stations designated as A (School), B (Imota), C (Idifi) and D (Aiyetoro) were selected along Ero reservoir, also four sampling stations were selected and designated as A (Odode), B (Church), C (Ayepe) and D (Dawodu) along Egbe reservoir for the purpose of this study. The reservoirs were sampled biweekly for analysis using five different gillnet mesh sizes 50.8mm, 63.5mm, 78.2mm, 88.9mm, and 101.6mm. The nets were set at 6.00pm and hauled in the morning at 8.00am, fishermen were well monitored by ensuring they set the gill nets at the sites at the same time to avoid sampling bias and ensure a constant fishing effort. The fishes caught with the nets were sorted into separate containers. The total length and weight of individual fish were taken. Simpson’s index, Simpson reciprocal index and evenness were determined. The percentage composition by (biomass) fish landing was recorded. Physico chemical parameter of the water was also studied. Altogether, 8646 fishes belonging to 2 families and 4 species were recorded at Ero reservoir while 31, 905 fishes belonging to 5 families and 7 species were recorded at Egbe reservoir. The most abundant family was the Cichlidae represented by 3 species, Oreochromics niloticus, Coptodon zillii, and Tilapia guineensis at the Ero and Egbe reservoirs. The study showed O.niloticus as the most dominant species in the reservoirs. Furthermore, the result of this study showed there was variability in the total catch for different months. Catch landed for different species of fish and effort varied. Higher catches were recorded in Wet season than in the Dry season. The fish species diversity using Simpson’s index, Simpson reciprocal index and evenness were recorded as 0.63, 0.64, 0.63 and 0.62 at Ero reservoir and 0.53, 0.63, 0.63 and 0.63 at Egbe water reservoir. There were more catches in terms of weight and number at Station A of each reservoir. Sex ratio indicated that higher proportion of females were caught for O.niloticus, C.zillii, and T.guineensis at Ero and Egbe reservoirs during the study except for H.niloticus and H.odoe . However, the overall sex ratios of sampled fish showed no significant (P > 0.05) difference from the expected 1:1 male to female sex ratio. Gill net mesh sizes 50.8mm and 63.5mm caught more fishes (by number and biomass) at both reservoirs, which might be due to the mesh sizes which had the ability to catch only species that had grown up to the sizes. The gill nets were size selective rather than species selective. Catch per unit effort is highest in all the species in the gill nets of 50.8mm and 63.5mm mesh sizes. Although, the gill nets were very effective in the fisheries of these reservoirs, they should be discouraged for artisanal fishing activities in the reservoirs. In view of the fact that the reservoirs are overexploited with the small gillnet mesh sizes being utilized by the fishermen, they should be encouraged to embrace the use of other gears like the hook and line, cast net and traps for their fishing activities for increased fishing period and enhanced income and also improve the fish yield of both reservoirs to ensure sustainable management.