Effect of fasting and refeeding on growth and body composition of red porgy,Pagrus pagrus L.*

Red porgies, Pagrus pagrus L., were fasted for 7, 14 or 28 days, and were then allowed to feed on pellets released from demand feeders. Biological responses during fasting and refeeding were examined. The factors considered were growth, organosomatic indices and proximate body composition (protein, fat, ash and moisture). Fasted red porgies lost weight and had higher relative weights of eviscerated body than control fish. Refeeding was accompanied by hyperphagy, which resulted in similar total food demand being shown by all groups. Fish which had been deprived of food displayed compensatory growth and the final weights of these fish at the end of the experiment were similar to controls. There were no significant changes caused by fasting in the relative proportion of body chemical components. Calculations based upon changes in protein and lipid content suggest that more protein than lipid is metabolized during the first phase (14 days) of a fast.