Effects of Partial Replacement of Fish Meal Protein by Microalgae on Growth, Feed Intake, and Body Composition of Atlantic Cod

A feeding trial was conducted with juvenile Atlantic cod Gadus morhua (initial mean weight, 40.7 g) in which a combination of dried Nannochloropsis sp. and Isochrysis sp. replaced fish meal protein in isonitrogenous, isocaloric diets. Three experimental diets (55% protein, 16.5% fat; calculated gross energy = 5,328 kcal/kg) were formulated to replace 0, 15, or 30% of dietary fish meal protein. At the conclusion of the 84‐d study, no differences in survival, feed conversion ratios, viscerosomatic indices, and n‐3 and n‐6 fatty acids in the muscle were found among the treatment groups. Feed intake and growth, which were proportional to the level of algal incorporation, were significantly reduced in the algae‐fed fish and were probably due to palatability problems. Feed intake improved in the fish fed the diet with 15% fish meal protein replacement as the study progressed, but hepatosomatic indices indicate that those fed the diet with 30% replacement were approaching starvation. Received July 13, 2010; accepted September 8, 2010