GASTRIC EVACUATION AND FEEDING IN THE GILTHEAD SEA BREAM REARED UNDERSEMI-INTENSIVE CONDITIONS

Gastric evacuation rates of the gilthead sea bream, Sparus aurata, fed with commercial pelleted food and polychaetes (Nereis diversicolor) w ere determined under experimental conditions. The estimated gastric ev acuation rate for pelleted food was 7.97% h(-1), with a total time of digestion of approximately 9 h. The respective values for the natural food were 6.24% h(-1), with a total digestion time of approximately 12 h. The daily consumption of fish reared in earth ponds in a semi-inte nsive aquaculture facility was estimated through 24h cycles performed between April and August. The daily consumption varied from 18.58 to 3 1.98 mg g(-1). There was a constant increase in the average daily cons umption per individual of 1.8-4.6 g (dry weight). During these cycles, samples of stomachs were taken and the contents preserved for further observation. The feeding behaviour of the reared fish was compared wi th a fish sample caught in the Ria Formosa lagoon. No common species w ere found between samples. A total of 38 prey were identified, which s uggests that the gilthead sea bream is a non-specific predator. Despit e the high abundance of natural prey in the ponds, the dependence of s ea bream on pelleted food was high.