EVALUATION OF MICRODIETS VERSUS FROZEN COPEPODS ON GROWTH, SURVIVAL AND SELECTED CHEMICAL COMPOSITION OF LARGE YELLOW CROAKER PSEUDOSCIAENA CROCEA LARVAE

Three newly developed microdiets (MDs: Diet 1, Diet 2 and Diet 3), one co-feeding diet (Diet 4, combined Diet 3 with frozen copepods) and frozen copepods (Diet 5) were tested for weaning large yellow croaker (Pseudosciaena crocea) larvae from 25 to 60 days after hatching (DAH). The highest final specific growth rate (SGR, 7.97%/d) and survival (40.0%) were observed in fish fed Diet 1, while those were the lowest in fish fed Diet 5 (4.15%/d and 20.4%, respectively). The survival of larvae fed Diet 4 showed no significant difference (P>0.05) from that of larvae fed Diet 1. However, SGR of larvae fed Diet 4 was significantly lower (PP>0.05) among fish fed the MDs, which was lower than that of fish fed Diet 4, but higher than that of fish fed Diet 5. Fish fed the MDs had significantly higher (PPP<0.05) in fish fed either Diet 4 or Diet 5 than that in fish fed the MDs. The exceeded C22:6n-3 (DHA) levels in fish compared to their corresponding diets were found in those fed either Diet 4 or Diet 5. Inversely, C20:5n-3 (EPA) and DHA levels decreased in fish fed the MDs relative to their proportions in MDs. These results showed that fish fed either Diet 4 or Diet 5 had higher efficiency of AA, DHA and EPA deposition than fish fed the MDs. This study suggested that large yellow croaker larvae could be successfully weaned by MD. Future research should be based on formula of Diet 1, since it was superior to Diet 2 and Diet 3. In addition, changes of digestive enzymes and digestive tract of large yellow croaker larvae fed different diets need to be investigated for an overall evaluation.