To completely replace the fish meal by a mixture of earthworm and maggot meals, experimental diets were tested during 42 days on Clarias gariepinus fingerlings. Five isoproteic and isoenergetic diets (40 % crude protein and 17.9 ± 0.3 kJ g-1) including the control diet (D1) based on fish meal, were formulated. All these diets satisfied the essential amino acids requirements of C. gariepinus fingerlings. These diets were tested on triplicate groups of 50 fishes (initial body weight: 3 ± 0.1 g) bred in tank (0.5 m 3). The approximate ratios 2:5; 1:4; 1:12 and 0:1 between the earthworm meal and the maggot meal were used, respectively, to formulate four diets D2, D3, D4 and D5 without fish meal. After the feeding period, significant differences (P \ 0.05) were observed on growth, feed utilization between control diet (D1) and test diets (D2-D5). Fish fed earthworm-and maggot-based diets were grown better than those fed the control diet. Survival and feed utilization were not significantly affected by the ratio between earthworm meal and maggot meal in the test diets. Lipid content was higher in carcass and fillet of fishes fed earthworm-and maggot meals-based diets than that of those fed fish meal-based diet. This study indicates that when the ratio 2:5 between the earthworm meal and the maggot meal is used to entirely replace fish meal and the ratio lysine/arginine of the diet is inferior to 1, the growth performances and feed utilization of Clarias gariepinus fingerlings are improved.

This study is carried out to characterize the CHU-MEL effluents discharged into the Cotonou lagoon to assess the potential hazards of these releases for this ecosystem. To achieve this goal, the effluents collected at the end of the spillways have been analyzed. The results obtained from the physicochemical and microbiological analysis made it possible to assess the quality of the effluents. The pH, temperature and conductivity measured in-situ are, on average, 6.65, 30.3 °C and 763 μS/Cm. The average contents of dissolved oxygen, nitrite, nitrate, ammonium and Nitrogen Total Kjedhal (NTK) are respectively 1.

La présente étude a été conduite pour apprécier le niveau de pollution des eaux du collecteur de Dantokpa (Cotonou-Bénin) par l'évaluation de la diversité phytoplanctonique en relation avec les caractéristiques physico-chimiques afin de faire ressortir le risque de leur rejet sans traitement dans la lagune de Cotonou. L'analyse des eaux usées prélevées au niveau de trois stations a révélé des teneurs élevées en orthophosphates et en minéraux azotés (ammonium, nitrate et nitrite), une forte conductivité électrique et un faible taux d'oxygène dissous. Au total, 39 espèces phytoplanctoniques ont été identifiées au microscope et sur la base des clés d'identification. Cette communauté hétérogène de phytoplancton se répartit dans 5 embranchements (Chlorophytes, Chrysophytes, Cyanophytes, Euglénophytes et Rhodophytes) et 9 classes dominées par les Cyanophycées et les Diatomophycées. La densité phytoplanctonique a été élevée avec une moyenne de 25760 cellules/ml. Les paramètres étudiés témoignent de l'abondance de l'azote, du phosphore et des matières organiques dans les eaux du collecteur. Il est donc nécessaire de les épurer avant leur déversement dans la lagune au risque de provoquer son eutrophisation.

The current study aims at evaluating the effect of experimental feed protein rate on growth and feed utilization in Hoplobatrachus occipitalis tadpoles. Six same-energy feed diets containing crescent protein rates (20, 30, 40, 45, 50 and 60 %) were formulated and tested on Hoplobatrachus occipitalis tadpoles though initial mean weight was 0.380 ± 0.004 g. Each diet was tested in triplicate for 24 days. 55 tadpoles was stocked per pond containing 30L water. Survival rates recorded ranged between 85.454 and 92.727% for all treatments. Growth and feed utilization parameters varied significantly with feed protein rate (P < 0.05). The best growth performances were recorded with 60% protein diet. According to the mathematical model (polynomial regression II) used for analysis of specific growth rate variations in relation to feed protein rate, optimal and maximal protein needs of Hoplobatrachus occipitalis tadpoles are 33 and 51% respectively. The highest protein rate of tadpoles' carcass was noticed in tadpoles fed on 45% protein diet. The highest rate of lipid and dry matter was observed in tadpoles fed on 50% protein feed. The optimum and maximum protein requirements for better growth of H. occipitalis tadpoles are 38.30% and 54.10%, respectively.

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