Observations on the Composition, Physiological Condition and Fisheries in Erinle Lake, Osun State, Nigeria

The level of fish production in Nigeria is far less than the current fish demand. The study, therefore, on fish composition and fishing activities in Erinle Lake is meant to suggest means of bridging the gap between fish supply and demand in the country. Fish samples were obtained from gill-net, cast net and traps. Ten families of fish comprising 19 species were identified, dominated by Cichlid fish (71%) largely made up of Sarotherodon galilaeus (42%). The sex-ratio of most fish in the lake tends to unity (1:1), suggesting reproductive stability. Condition factors are high for the fish species – an indication that they thrive well in the habitat. Key water quality parameters such as pH, DO, etc. were found to be favourable for survival and thriving of food for some fish species. Fishermen on the lake used 2.54 cm mesh size net contrary to 7.62 cm mesh size recommended in Sea Fishing Regulations of 1971, which is a supplement of Nigerian Sea Fisheries Decree (ACT) of 1971. As a result the lake had been exploited of fish resulting in a low and small size catches. It is recommended that the fisheries be closed during the peak spawning period to allow possible recovery. Also, strict monitoring control and surveillance of the lake is highly recommended, most especially in the use of unapproved fishing nets and methods. TABLE 1 A checklist of fish species in Erinle lake between November 2006 and May 2008 Family Genus/Species Common name Alestidae Alestes longipinnis Gunther African tetra Alestes macrolepidotus Guvier & Valenciennes African tetra Bagridae Bagrus bayad macropterus Daget Bagrid Channidae Parachanna obscura Gunther Snake head Characidae Chrysichthys auratus Pfaff Characines Cichlidae Hemichromis faciatus Peter Banded jewel fish Oreochromis niloticus Linnaeus Nile Tilapia Pelmatochromis guntheri Sauvage Sarotherodon galilaeus Trewavas Mango Tilapia Tilapia mariae Boulenger Tilapia melanopleura Tilapia zillii Gervais Red belly Tilapia Clariidae Clarias gariepinus Burchell African cat fish Cyprinidae Labeo coubie Ruppell African cap Hepsetidae Hepsetus odoe Bloch African pike Mormyridae Mormyrus rume Cuvier & Valenciennes Elephant nose fish Gnathonemus cyprinoides Linne Gnathonemus senegalensis Steindachner Schilbeidae Schilbe mystus Linnaeus African butter fish