Estimated amino acid requirements during early ontogeny in fish with different life styles: gilthead seabream ( Sparus aurata) and Senegalese sole ( Solea senegalensis)

Abstract

Little is known about the amino acid (AA) requirements of larval fish and their possible ontogenetic changes. This paper aims to contribute to the study of these requirements in two common cultured species in Southern Europe: gilthead seabream ( Sparus aurata) and Senegalese sole ( Solea senegalensis). Moreover, it is intended to identify possible dietary AA imbalances occurring in normal hatchery conditions for both species. Fish larvae were reared following standard procedures and the normal feeding schemes used in hatcheries, which includes the use of live prey for several weeks. The experiments were finished once the fish were adapted to a dry feed. Samples were collected at different points for dry weight, total protein, and AA analysis. The A/E ratios [each indispensable AA content×(total indispensable AA content including cysteine and tyrosine) −1×1000] of fish and food were compared to identify possible dietary AA imbalances. The AA profile of both fish species changed during ontogeny, but was more stable during seabream than Senegalese sole development. This is probably linked to the marked metamorphosis observed in sole. These changes in fish larval AA profile suggest that the AA requirements change during seabream and Senegalese sole ontogenesis. Several dietary AA deficiencies were found during the ontogenetic development of both species. These deficiencies result from ontogenetic changes in the fish AA profile, but also from differences in the AA composition of the different food items. These results suggest that both the live food (rotifers and Artemia at different developmental stages) and the dry feed used in the rearing of gilthead seabream and Senegalese sole does not have an AA profile that entirely meets the requirements for the early stages of these species.