Abstract
The freshwater cichlid, Sarotherodon galilaeus (Linne, 1758) is an economically and commercially important fisheries species that has naturally colonized and dominated a sand-dragged man-made freshwater lake of Ahozon (South-Benin) where the species made about 85.21% of the fish community. We investigated the feeding ecology of S. galilaeus in order to evaluate resource exploitation and the establishment of this species in Lake Ahozon. During wet, flood and dry seasons, 1189 individuals of S. galilaeus have been monthly sampled in the open water and in the aquatic vegetation habitats. The study showed that S. galilaeus consumed about seventy (70) food items dominated by algae (52.88%) composed of 28 families and 52 genera from blue-green algae, green algae, desmids, and diatoms, sand particles (23.95%), detritus (12.27%) and protozoans (7.68%). Minor preys were rotifers, copepods, cladodera, crustacea and insect parts. Foods items with higher diet occurrence were sand particles with a percentage occurrence of 72.33%, detritus (69.47%), and some algae such as Scenedesmus (58.96%), Closterium (55.68%), and Microcystis (51.30%). Significant (P ≤ 0.05) ontogenetic variations of empty stomachs were recorded. S. galilaeus exhibited a wide diet breadth (DB) ranging between 5.55 and 7.29 that tended to increase with fish sizes. Diet overlaps (Ojk) varied from 0.77 to 0.97, indicating high diet similarities between different life stage categories. The slope b = 0.560 obtained from Log (body weight)-Log (gut length) linear regression, and the mean ratio of GL/SL = 6.72 ± 2.23 support our findings that S. galilaeus exhibited detritivorous, herbivorous and omnivorous food habits. The broad spectrum of food resources consumed/utilized and the high diet breadth recorded leading to allometric growth, the active breeding and the high propagation of the species, were some indicators of the successful establishment of S. galilaeus in the man-made lake of Ahozon. Sustainable fisheries/ aquaculture exploitation of S. galilaeus and successful valorization of the man-made lake of Ahozon require an integrated management of the lake including the prevention of domestic waste dumpings, the protection of the foraging and spawning grounds, the fertilization of the lake, the introduction of predators to control the population of S. galilaeus , the protection of lake margin to avoid erosion, a planned harvest of the fish stock and a periodic ecological monitoring of Lake Ahozon.
Highlights
The freshwater cichlid, Sarotherodon galilaeus (Linné, 1758) is an economically and commercially important fish resource occurring in some natural freshwater bodies of Benin, such as Lakes Toho-Todougba, Dati, Ahouangan, the man-made lake from a sugar industry (SUCOBE), rivers such as Sô, Oueme, Niger and floodplains [1] [2]
Nothing is known about the feeding ecology of this tilapine cichlid in this abandoned and neglected artificial lake originated from a progressive accumulation of running water in an extensive hole created by sand-dragging activities
The present study indicated that S. galilaeus consumed about seventy (70) food resources composed of a variety of benthic and pelagic prey items dominated by algae (52.88%) constituated of blue-green algae, green algae, desmids and diatoms, sand particles (23.95%), detritus (12.27%) and protozoans (8.69%)
Summary
The freshwater cichlid, Sarotherodon galilaeus (Linné, 1758) is an economically and commercially important fish resource occurring in some natural freshwater bodies of Benin, such as Lakes Toho-Todougba, Dati, Ahouangan, the man-made lake from a sugar industry (SUCOBE), rivers such as Sô, Oueme, Niger and floodplains [1] [2]. In Southern Benin, S. galilaeus has naturally colonized and dominated a sand-dragged man-made freshwater lake of Ahozon Village (Ouidah City, County of Pahou) where the species reproduce actively, made about 85.21% of the fish community, and appears to be well-established in this artificial lake [3] [4]. Feeding ecology is important to understand the dynamic and the structure of the population, and to evaluate the establishment of S. galilaeus in this special habitat, the sand-dragged man-made lake of Ahozon [12] [13]
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