Evaluation of short and long term enrichment of Artemia franciscana with mixed algae or DHA oil emulsion for improving Dicentrarchus labrax larvae aquaculture

Abstract

Setting up nutritional requirements with high-quality, time-saving marine finfish larvae is a big issue for increasing aquaculture profit. In the current study, we evaluated the nutritional value of two enrichment diets [DHA oil emulsion-enriched Artemia (Art-DHA-Selco) and mixed algae-enriched Artemia (Art-MA)] and two-timing protocol (2 & 24 h) for serving European Sea bass. Larval growth performance and survival percentage, as well as biochemical compositions of the enriched Artemia and for the fed larvae after 25 rearing days, were determined. The results revealed that survival percentage (S%), feed conversion ratio (FCR), and protein efficiency ratio (PER) was insignificantly affected by the two factors (diets and time) or the interaction between them. Otherwise, growth in terms of final body weight (FBW), specific growth rate (SGR) as well as productive protein value (PPV) differed significantly at (P ≤ 0.01) among treatments in both factors. Concerning biochemical analysis, the highest protein value was recorded in Art-MA at 24 h. In contrast, lipid and carbohydrate levels were considerably higher in Art-MA 2 h than in the Art-DHA. That decrease in protein content, FBW, and SGR in the 2 h period in the MA treatment may attribute to the smaller size of the Artemia metanauplii in the 2 h than those after 24 h. That can be overcome by starting with Artemia metanauplii at the end with Instar II before enrichment process so that the size is big enough to give better results. The results revealed that PUFAs percentages were significantly highest especially EPA percentage in the enriched Art-MA 2 h followed by its correspondence Art-MA at 24 h compared with Art-DHA or un-enriched ones. Otherwise, the fatty acid composition (FA) of post-larvae surpassed greatly in EPA and n3/n6 ratios as diet reflection in the algal short-term duration. Based on the results and the documented drawbacks of DHA-Selco, the authors recommended using mixed algae in the enrichment protocol for feeding larval stages over the short term.