Feeding, physiology and growth responses in first-feeding gilthead seabream (Sparus aurata L.) larvae in relation to prey density

21 The effects of prey density (0.1, 1 and 10 rotifer ml ) on feeding, oxygen uptake, growth, survival and energetic efficiencies in Sparus aurata larvae were investigated. Dry weights and 21 total lengths at day 15 after hatching were similar in larvae fed with 10 and 1 rotifer ml but 21 were significantly higher than in larvae fed with 0.1 rotifer ml . These differences were a consequence of a delay in starting feeding and growth in larvae fed with the lowest rotifer 21 concentrations tested. Growth rates were similar in larvae fed on 0.1 and 1 rotifer ml , while 21 larvae fed with 10 rotifers ml showed the smallest growth rate. Survival decreased markedly (from 91 to 7%) when prey density decreased. Ingestion rates of the actively feeding larvae 21 increased with age at the three prey densities but larvae fed with 0.1 rotifer ml showed lower ingestion rates. The specific oxygen uptake increased from hatching up to 35–40 mg dry weight; above this size the specific oxygen consumption remained almost constant. Survival at the end of the experimental period was closely related to the percentage of larvae able to start feeding at day 21 6. In larvae fed with 0.1 rotifer ml , the energy ingested during the first days of feeding roughly met maintenance requirements. Therefore, the survival of larvae able to start feeding is not guaranteed at such low prey density.  2000 Elsevier Science B.V. All rights reserved.