The effect of competition on the feeding efficiency and feed handling behaviour in gilthead sea bream (Sparus aurata L.) held in tanks

The aims of this study were to determine whether growth, feed handling and feeding efficiency of gilthead sea bream (Sparus aurata) changed in response to imposed competition levels, manipulated by altering ration and feed delivery rate, and to investigate the effect of feed handling on feed conversion efficiency. Triplicate tanks of bream (32 g, 12 kg m(-3)) were fed rations of 3.5%, 3%, 2.5% or 2% BW day(-1) at a rate of ca. 10 g min(-1), in three meals. To compare the effect of feed delivery rate, triplicate tanks were fed a 3% BW day(-1) ration at a rate of ca. 20 g min (-1). Low rations increased competition levels; feeding intensity, density of fish under the feeder and frequency of sharp-angled turns increased during meals. Increasing the feed delivery rate had a weaker influence on competition; feeding intensity was higher and sharp angled turns more frequently observed but fish density under the feeder increased and swimming speeds decreased during feeding for both feed delivery rates tested. Increasing ration and feed delivery rate led to an increase in feed intake, growth rate, rate of chewing and proportion of feed particles in the stomach. High feed delivery rate also appeared to result in a reduction in waste from chewing. Bream fed the 3% BW day 1 ration (just under satiation) delivered at a high rate had the lowest standard FCR. This was also true for when calculating FCR, taking into account the actual feed intake. However, when taking waste from handling feed into account, the resulting FCRs were higher in treatments where waste from chewing was reduced i.e. for bream fed at the high rate of feed delivery. The results are discussed in terms of improved feeding practices for the intensive culture of this species. (C) 2004 Elsevier B.V. All rights reserved.