Early-weaning diets for gilthead sea bream (Sparus aurata L.) and their potential use in Hellenic marine fish hatcheries
The purpose of this experiment has been to evaluate the suitability of commercially available early-weaning microdiets (MDs) for the production of sea bream early juveniles and in comparison with late-weaning protocols already in use by Hellenic marine fish hatcheries. Four sea bream experimental groups were allocated in rearing tanks of a commercial Hellenic marine fish hatchery. Each group represented a different protocol (A, B, CA, and CB) based on the combination of two different early-weaning MDs (A and B) and a late-weaning diet (C). In addition, the late-weaning protocols have received Artemia instar II only and not Artemia instar I. In protocol A, Artemia instar I first feeding and the early-weaning diet A were administered at 17 days post-hatch (17 dph). In protocol B, Artemia instar I first feeding started at 15 dph and the early-weaning diet B was administered at 18 dph. In the C protocols, Artemia instar II first feeding started at 20 dph and the early-weaning diets (A or B) were administered at 25 dph. All protocols have received the late-weaning diet C only after the 50th dph. The experiment lasted for 65 days. By the end of the experiment, early-weaning protocol A and late-weaning protocol CB had similar wet weights, but still lower to the wet weights recorded for the late-weaning protocol CA. These results cannot be explained solely by the nutritional profile of each weaning diet. The larval fatty acid profile of each protocol and at various time intervals reveals the importance that the succession of Artemia, rotifers, and MDs has for each protocol and not just the nutritional profile of the weaning diets, per se.