BIOECONOMIC ANALYSIS OF FISH GROWTH - EFFECTS OF DIETARY-PROTEIN AND RATION SIZE

Computer experiments were performed with a bioenergetic model for channel catfish (Ictalurus punctatus) to determine the nature of interactions between ration size and dietary protein from biological and economic standpoints. Both ration size and dietary protein exhibited decreasing magrginal products, as expected from the law of diminishing returns. Dietary protein has a positive effect on feed efficiency (except at combinations of high protein and high rations), while ration size did not seem to affect protein efficiency. Isoquant analysis showed that dietary protein and ration size are substitute inputs within a certain range, implying that the same harvest weight can be obtained by feeding low protein diets at high rations or high protein diets at low rations. Cost was minimized with dietary protein ranging from 26.5 to 34.2% of the diet and rations ranging from 0.79 to 1.0 of satiation, depending on the protein non-protein price ratio of the diet. © 1990.