Author(s)

Youssouf Abou, Aliou Saidou, Daouda Mama, Emile D. Fiogbé, Jean-Claude Micha

Laboratory of Applied Hydrology, Faculty of Sciences and Technics, University of Abomey-Calavi, Abomey-Calavi, Republic of Benin.
Laboratory of Soil Sciences, Department of Crop Production, Faculty of Agricultural Sciences, University of Abomey-Calavi, Abomey-Calavi, Republic of Benin.
Research Unit in Environmental and Evolutionary Biology, FUNDP-University of Namur, Namur, Belgium.
Research Unit on Wetlands, Department of Zoology and Genetic, Faculty of Sciences and Technics, University of Abomey-Calavi, Abomey-Calavi, Republic of Benin.

Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2% crude protein) and isoenergetic (16.9 Kj·g^–1) diets A₀, A₁₀, A₂₀, A₃₀, A₄₀ and A₅₀, containing 0%, 10%, 20%, 30%, 40% and 50% of Azolla meal (AM) respectively, as partial fishmeal (FM) substitutes, was provided to experimental fish. The Azolla-free diet A₀ served as a control. Fish specific growth rate (SGR) was higher with the control diet, the lower values being obtained in A50-fed fish (P < 0.05). Crude protein and P content in experimental fish showed similar values. Evaluation of the nutrient wasted show identical values (84.8% - 87.8% of supplied) for total P (TP); while total N (TN) discharged into ponds by fish increased significantly when AM level greater than 30% in diets (P < 0.05), amounting 63.9% - 74.2% of that supplied. From these findings, the fern Azolla could be used in diet to sustain Nile tilapia growth and as “environmentally-friendly” ingredient to limit P loss, while providing N to the field, beneficially in tropical marshland pond where this nutrient is already limiting.

Azolla; Aquaculture; Environment; Fish Meal Replacement; Oreochromis niloticus; Nitrogen; Phosphorus; Nutrient Balance

Abou, Y. , Saidou, A. , Mama, D. , D. Fiogbé, E. and Micha, J. (2012) Evaluation of Nitrogen and Phosphorus Wastes Produced by Nile Tilapia (Oreochromis niloticus L.) Fed Azolla-Diets in Earthen Ponds. Journal of Environmental Protection, 3, 502-507. doi: 10.4236/jep.2012.36060.