Abundance, length – weight relationships and Fulton’s condition factor of the freshwater cichlid Sarotherodon galilaeus (Pisces: Teleostei: Perciformes) from a sand-dragged man-made lake of Southern Benin, West Africa
By: Houehanou M.A.G. Gbaguidi, Alphonse Adite
Key Words: Artificial lake, Condition indices, Establishment, Fisheries, Length-weight model.
J. Bio. Env. Sci. 8(5), 75-87, May 2016.
Condition factors and growth trends indices such as allometry coefficients are decisive fisheries management tools that evaluate the well-being of fishes, their establishment and the quality of their habitat. We investigated the condition factors and length-weight relationships of a freshwater tilapine cichlid, Sarotherodon galilaeus, that has naturally colonized the artificial lake of Ahozon (South-Benin). S. galilaeus individuals has been sampled every month in the “aquatic vegetation” and in the “open water” habitats with seines, cast nets, gill nets and hooks. This species dominated Lake Ahozon and made about 85.21% of the fish community. Fish sizes showed significant spatial (F1,5548=57106.9, p=0.0001) and seasonal (F2,5547=82,06, p=0.0001) variations and smaller sizes (18.65±5.76mm-SL) were recorded in the “aquatic vegetation” considered as the spawning ground for S. galilaeus. In Lake Ahozon, length-weight regression equations gave slopes b ranging between 2.636 and 3.081 indicating that S. galilaeus exhibited both allometric and isometric growth. Also, the species exhibited spatial (F1,5548=94.510, p=0.0001), seasonal (F2,5547=7.163, p=0.001), ontogenetic (F2,5547=63.591, p=0.0001) and sexual (F1,3781=8.275, p=0.001) variations of condition factors (K) that mostly depend on the availability of food resources. The prominence of the species and its condition factors indicated that S. galilaeus is well- establishment in Lake Ahozon. The improvement of growth performance and well-being for a sustainable fisheries/aquaculture in Lake Ahozon require the protection of the foraging and spawning grounds, the prevention against organic and chemical pollution, the introduction of predators to prevent overpopulation of S. galilaeus, the fertilization of the lake and a planned harvest of the fish stock.