Effects of feeding levels on growth response, body composition, and energy expenditure in blackspot seabream, pagellus bogaraveo, juveniles

Although reported as a slow growing species, to date information regarding nutritional dynamics of blackspot seabream, Pagellus bogaraveo, is limited, especially during ongrowing phase. This study determined the effects of different feeding levels on growth response, body composition, and energy expenditure of blackspot seabream juveniles (initial weight = 64 g). Fish were allocated in nine indoor tanks (15 fish per tank) and fed a basal diet twice daily at increasing levels (2.5, 3.3, and 4.1 g feed/kg(0.8)/d) for 138 d. Growth response decreased with decreasing feeding levels, but only at 2.5 g feed/kg(0.8)/d (P < 0.001). Differences in growth rates were positively correlated with body lipid content (r(2) = 0.90). Net protein utilization decreased with each increase in feeding level. The energy requirement for zero growth (maintenance) and the estimated energy loss on starvation were calculated as 22.6 and 17.9 kJ/kg(0.8)/d, respectively. The energy cost for protein and lipid gain was calculated as 3.8 and 1.4 kJ/kJ energy deposited, respectively. This study suggested that blackspot seabream may grow slower than the other close-related species because of its higher demand of dietary protein energy in favor of lipid deposition.Portuguese Foundation for Science and Technology [POCTI/CVT/39239/2001]