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 (initial body weight 3.5 g), held in 500-1 tanks under a mbient temperature and natural light, and fed according to the following me thods: by automatic feeders that released feed continually in daylight acco rding to feed manufacturers' recommendations (AF100%); half of the above co ntinually in daylight (AF50%); half of the above again but in two meals onl y (AF50%M); and by self-feeders that supplied feed at low (SFL), medium (SF M) and high (SFH) reward. None of the feeding conditions affected the survi val rate of fish. SFL fish had the highest specific growth rate, while AF50 % and AF50%M the lowest. Population weight distribution in the restricted a utomatic-fed fish (AF50% and AF50%M) was more homogenous compared to the ot her feeding conditions. These two practices produced high feed efficiency r atios (0.93 and 0.95, respectively), compared 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(-1) could be considered as the optimum feeding practice, comb ining 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 th eir manipulation of the self-feeders according to their feed needs. Daily f eeding activity in all self-fed fish groups was independent of feeding rewa rd. (C) 2000 Elsevier Science B.V. All rights reserved.