The development of balanced fish feeds that consider the nutritional requirements for the early stages of fish larvae is essential to promote optimal growth, enhance feed conversion efficiency, while ensuring high survival rates and good quality juveniles. An inert diet that is well ingested, digested and assimilated by larvae at mouth opening, has long been an objective of fish larvae researchers. Currently artemia replacement diets are a widely used feeding strategy in fish larviculture since inert diets are easier to use and have a stable composition, whereas the composition of live feed can vary according to culture and enrichment conditions. The main objective of this work was to assess the effect of an artemia early weaning with an inert diet in European seabass (Dicentrarchus labrax) larvae development. To this end, a feeding trial was conducted for 40 days, during which fish at 12 days after hatching (DAH) were fed one of two experimental diets: a live feed diet with standard weaning (CTRL), and the same life feed diet but with early co-feeding diet (EARLY), where the amount of live prey is reduced (vs the standard regime) and replaced by inert microdiets (fig. 1). In the CTRL group the amount of microdiet is gradually replaced from 17 to reach 100% at 35 DAH. At the end of the feeding trial (40DAH), all tanks are fed with a common microdiet and growth-related gene expression, biometry and survival were analysed.
Interestingly, the results show differential expression of growth-related genes such as growth hormone (gh), GH receptor (ghrb), insulin growth factor 2 (igf2), IGF receptor (igfr), and peroxisome proliferator activated receptor alpha (ppara) in the early weaning condition. This may highlight the potential of these genes as growth biomarkers to predict growth rate. Since the trial was conducted for only 40 days, it would be interesting to follow the growth of these fish for a longer period (e.g. 70 DAH). Overall, these results indicate that an early weaning in European seabass (Dicentrarchus labrax) farming might affect larvae performance in the early stages of development as well as later on in fish development, as described in previous work with other fish species.
This study had the support of the projects PACTO DE INOVAÇÃO BIOECONOMIA AZUL (Project No. C644915664-00000026) and INOVAQUA (MAR-021.1.3-FEAMPA-00004). The technical assistance of EPPO and S2AQUAcoLAB staff was highly appreciated throughout the study.