Résumé
Labeo rohita, Gibelion catla, Cirrhinus mrigala, Ctenopharyngodon idella and Hypophthalmichthys molitrix were grown together for 365 days in triplicate ponds. Six iso-caloric feeds having varying protein levels i.e. 22, 24, 26, 28, 30 and 32% were prepared and supplemented to fish at 2% fish weight daily. Significantly, higher final average weight [793 +/- 197 g] and total length gain [398 +/- 40 mm] was recorded for Ctenopharyndodon idella. Net fish yield enhanced as the level of digestible protein [DP] in the supplementary diets increased and plateaued at 28% DP level, thereafter significant reduction [P<0.05] in fish weight increments was experienced at any surplus protein level. Among the supplementary feeds, 28% DP level resulted in maximum net fish yield [4304 +/- 33 kg ha-1 year-1] and a significantly higher overall nitrogen conversion ratio [NCR] of 1:5.2 +/- 0.14. Higher level of DP in supplementary feeds resulted in reduced fish growth