Energy and protein requirements of yellowtail for maximum growth and maintenance of body weight

Abstract

Three feeding experiments were conducted pragmatically to determine energy and protein requirements of different sized yellowtail (31, 94, and 506 g on average) for maximum growth and maintenance of body weight under different water temperatures (29.8, 27.1 and 18.8°C on average) in small net cages. Fish were fed to satiation or at levels between 10 and 70% of the satiation level or at body weight maintenance levels or starved. The experimental diets were extruded dry pellets with known digestible energy (DE) and protein (DP) values. The growth rate was highest for the satiation group and decreased proportionally to the feeding levels. The DE and DP requirements for maximum growth were 206 kcal and 22.5 g, 274 kcal and 27.3 g, and 82 kcal and 7.7 g/kgBW per day, respectively, for fish with the initial body weight of 31, 94, and 506 g; while the requirements for maintenance of body weight were 31 kcal and 3.4 g, 31 kcal and 3.1 g, 29 kcal and 2.7g/kgBWper day, respectively. Both the requirements for maintenance of body energy content were significantly higher than those for maintenance of body weight.