THE EFFECTS OF A TEMPERATURE RISE ON OXYGEN-CONSUMPTION AND ENERGY BUDGET IN GILTHEAD SEA BREAM

The rates of daily average, minimum and maximum oxygen consumption, sp ecific dynamic action (SDA), ingestion and digestibility in gilthead s ea bream, Sparus auratus L., were measured before, during and after a gradual rise of water temperature from 20 to 28 degrees C at a rate of I degrees C day(-1). The relationship between energy gain and the met abolic costs has also been investigated. Oxygen consumption of juvenil e sea bream had a clear daily rhythmicity, with low levels during dark ness and higher levels during the light period. Both light and feeding processes raised the metabolism of sea bream, but fish fasted for 2 d ays also showed an increase in oxygen consumption during the light per iod. Acclimation to 28 degrees C was complete for the minimum oxygen c onsumption rate in 12 days, but daily average and maximum oxygen consu mption rates on the 19th day after the change were still 33% higher th an at 20 degrees C mainly due to increased SDA. The digestibility of f ood components did not change significantly throughout the experiment. These relationships are discussed with respect to the potential for g rowth when fish are reared at 28 degrees C, although the energy costs are high.