Effect of Food Particle Size, Stocking Density and Feeding Frequency on the Growth Performance of Juvenile Korean Rockfish Sebastes schlegelii

摘要

We performed four sets of feeding trials to establish optimum feed size (Exp-I), stocking density (Exp-II) and feeding frequency (Exp-III and IV) for Korean rockfish. In Exp-I, three different particle sizes of a commercial diet (small, 2.0-2.1 mm; medium, 2.4-3.2 mm; and large, 4.0-5.3 mm) were fed to four replicate groups offish (22.8±0.1 g), each of which was fed to apparent satiation for six weeks. In Exp-II, fish (44.3±0.4 g) were reared at four stocking densities (1.5, 3.0, 4.5 and 6.0 kg/m~3) and fed a commercial diet to apparent satiation for four weeks. In Exp-III, fish (14.8±0.1 g) were fed a commercial diet once, twice, thrice, 4x or 5x a day at a feeding ratio of 3.25% of body mass. Another group of fish was fed the same commercial diet 5x a day to apparent satiation; this treatment was designated FS (five times satiation/day). In Exp-IV, fish (31.3±0.1 g) were fed a commercial diet once, twice, thrice or 4x a day to apparent satiation. Another group of fish was fed to apparent satiation once every 48 hours. In Exp-I, fish fed the large particle (4.0-5.3 mm) diet had a significantly higher feed conversion ratio and lower protein efficiency ratio than fish fed the small particle diet. In Exp-II, groups of fish reared at densities of4.5 and 6.0 kg/m~3 had significantly higher feed intake and growth performance than fish reared at 1.5 and 3.0 kg/m~3. In Exp-III, fish fed to apparent satiation had significantly higher growth performances than fish fed once or 4x a day. A significantly higher feed conversion ratio and a lower protein efficiency ratio were obtained in the FS group. In Exp-IV, growth performance and feed utilization efficiency were not significantly affected by experimental variation in feeding frequency. Fish fed to apparent satiation once every 48 hours had better feed utilization than those in other treatments and growth performances of those were comparable. Therefore, the optimum feed particle size, stocking density and feeding frequency for Korean rockfish underconditions we used were 2.0-3.2 mm, 4.5-6.0 kg/m~3, and once a day or once every 48 hour, respectively.