Dietary protein, growth, nutrient utilization and body composition of juvenile blackspot seabream, Pagellus bogaraveo (Brunnich)

When considering new marine species for Mediterranean aquaculture, blackspot seabream emerges as a potential candidate. However, there are scarce data on the nutritional requirements and optimal growth conditions of this species. A 12-week feeding trial was conducted to evaluate the effects of dietary protein on growth, nutrient utilization and body composition of blackspot seabream (23 g). Five isolipidic diets (12%) with graded levels of protein (20-60%) were distributed, twice a day, to duplicate groups of fish, until satiation. Growth increased significantly with increasing dietary protein up to 40%, but higher protein levels induced a similar daily growth index (1.4). Feed conversion ratio (FCR) decreased with increasing levels of dietary protein (4.2-1.6). No significant differences were detected in protein of whole body blackspot seabream among treatments, but fat percentage decreased with increasing dietary protein. Dry matter and energy digestibility showed a concomitant increase with the reduction in dietary wheat meal, attaining maximal values with high protein diets. These results suggested that the most favourable values for growth and FCR are obtained with diets containing 40% protein. However, the excessive lipid deposition reveals that more nutritional studies are necessary before the species can be established in aquaculture