A winter-based assessment on energy and protein requirements of yellowtail at the optimum feeding frequency

Abstract

In order to determine the energy and protein requirements of yellowtail during the winter season, two feeding experiments were conducted in net cages during the winters of two subsequent years. The cages were located at three different environmental conditions in Mie, Oita, and Wakayama Prefectures, Japan. At the locations, commercial soft-dry pellets (SDP) with known digestible energy (DE) and protein (DP) values were fed to satiation to four groups of fish either for five, three, two, or one time(s) per week. In the first experiment, fish fed three times per week produced the best growth in Mie and Oita Prefectures. The respective daily DE and DP requirements per kg body weight (BW) were found to be 40.7 kcal and 3.3 g in Mie and 30.4 kcal and 2.5 g in Oita. In the second experiment, fish fed five times per week showed slightly higher growth and feeding rates in Mie and Oita Prefectures. The requirements of DE and DP were 43.7 kcal and 3.3 g/kgBW/day in Mie and 35.9 kcal and 2.7 g/kgBW/day in Oita. In Wakayama, fish fed three times per week showed the best growth. DE and DP requirements were 40.5 kcal and 3.1 g/kgBW/day, respectively. These results, along with observations on stomach evacuation suggest that a feeding frequency of three times per week would be adequate for yellowtail during the winter season.