European sea bass growth and N and P loss under different feeding practices

This study was performed to assess growth rate, feed efficiency, and N and P loss of sea bass Ž . initial body weight 3.5 g , held in 500-l tanks under ambient temperature and natural light, and fed according to the following methods: by automatic feeders that released feed continually in Ž . daylight according to feed manufacturers’ recommendations AF100% ; half of the above continuŽ . Ž . ally in daylight AF50% ; half of the above again but in two meals only AF50%M ; and by Ž . Ž . Ž . self-feeders that supplied feed at low SFL , medium SFM and high SFH reward. None of the feeding conditions affected the survival rate of fish. SFL fish had the highest specific growth rate, while AF50% and AF50%M the lowest. Population weight distribution in the restricted automaticŽ . fed fish AF50% and AF50%M was more homogenous compared to the other feeding conditions. Ž . These two practices produced high feed efficiency ratios 0.93 and 0.95, respectively , compared Ž . Ž . to the AF100% 0.57 and self-fed ones SFL: 0.60; SFM: 0.37; SFH: 0.21 . Self-feeding at low reward of 0.6 g trigger could be considered as the optimum feeding practice, combining higher weight gain, lower N and P loss, and intermediate feed supply compared to the other treatments. In the SFH method, fish did not adjust their manipulation of the self-feeders according to their feed needs. Daily feeding activity in all self-fed fish groups was independent of feeding reward. q 2000 Elsevier Science B.V. All rights reserved.