The status of fish diversity and fisheries of the Keta lagoon, Ghana, West Africa
The fish and fisheries of three fish landing sites around the Keta lagoon in Ghana have been studied. A total of 18 fish species belonging to 13 families were encountered in the study. Four of the species were found to be commercially important notably, the cichlids (Tilapia guineensis and Sarotherodon melanotheron), the Bonga shad, (Ethmalosa fimbriata) and the blue-swimming crab, (Callinectes amnicola). The most important shell fish was the blue swimming crab (Callinectes amnicola). All the fishes showed isometric growth values from 2.6 to 3.0. Mean monthly condition factor (K) was between 0.3 ± 0.5 and 13.9 ± 1.8. Occurrence of fish species caught in commercial fishing was 32.3 per cent for Callinectes amnicola, 18.5 per cent for Tilapia guineensis and 13.9 per cent for Sarotherodon melanothron. Total weight of fish caught in experimental fishing was 2.7 tonnes. From experimental fishing with cast nets, Ethmalosa fimbriata accounted for 41.8 per cent (percentage of occurrence) of the total catch, whilst T. guineensis accounted for 29.2 per cent, Sarotherodon melanotheron accounted for 23.3 per cent and Callinectes amnicola accounted for 5.7 per cent. Shannon-Wiener species diversity of fish species was highest in Woe (0.76), followed by Anloga (0.46) and least in Anyanui (0.14). The Keta lagoon was found to be an important nursery ground for some juvenile marine species including Clupeidae, Mugilidae, Lutjanidae, Peneidae, Carangidae, Sciaenidae and Pomadasyidae. The most occurred fishing gears were the brush parks (Acadja) (29.1 %) and basket traps (23.2 %), whilst the least occurred gear was the encircling net (1.8 %). There is the deployment of multiplicity of fishing gears which was highly pronounced at Anloga where fishing appeared to be a daily source of income. Fisheries in the Keta lagoon are threatened from irresponsible fishing and environmental degradation. Management strategies that could be applied to enhance fishery productivity include re-establishment of estuarine conditions, preservation of vital habitats such as vegetation cover around the lagoon, and the development of aquaculture.