Determination of an optimal daily dietary ration for large two-year-old mulloway (Argyrosomus japonicus) using current commercial feed management practices

A 30 day tank feeding trial was conducted to determine the optimal dietary ration for large (initial size and length, 1.7 kg, 54.27 cm) two-year-old mulloway (Argyrosomus japonicus) grown in seawater during winter (July-August, water temperature 17.01–20.58°C). Mulloway fed at 0.6% body weight (BW) day-1 were underfed while feeding at 1.0% BW day-1 produced significant wastage, with up to 25% of the weekly ration uneaten. Differences in growth were also evident; fish fed at 0.8 and 1.0% BW day-1 grew significantly faster (SGR, 0.33 and 0.34% day-1, respectively) than 0.6% BW day-1 (SGR, 0.23% day-1). Mulloway fed at 0.8% BW day-1 had the highest condition index (1.14), feed conversion efficiency (78.6%) with minimal wastage (0.31- 2.1% of weekly ration un-eaten). The results of this study suggest that using a feeding rate of 0.8% BW day- 1has the potential to maximize growth, reduce feed wastage and lower costs of mulloway production.