Effects of four natural diets on the culture performance and biochemical composition of megalopa of Eriocheir sinensis during desalination period

Abstract

Frozen copepods, frozen adult Artemia, live rotifers and live Artemia nauplii were used as feed for the megalopa of Eriocheir sinensis during desalination stage to determine the most nutritious and cost-effective feed. The biochemical composition of the four feeds was analysed. Then, the individual wet weight, individual dry weight, survival rate, the cost and the biochemical composition of the megalopa were measured after the desalination. The resulting effects on the metamorphosis ratio and the duration of the megalopa were also assessed. The results showed that the duration of desalinated megalopa to first stage crab for all treatments was approximately 3.5 days, while the metamorphosis rate of the copepod treatment was significantly higher than the other treatments with the value of 96.33 ± 3.79%. In terms of biochemical composition, after desalinization, the moisture content of megalopa in the adult Artemia treatment was the highest, and the total lipid in the Artemia nauplii treatment and rotifer treatment was significantly higher than the other two treatments. The desalinated megalopa from copepod treatment had the highest percentages of DHA (22:6n-3) and EPA (20:5n-3) among the four treatments. The desalinated megalopa from copepod treatment and rotifer treatment had the higher contents of protein. In conclusion, frozen copepods have higher nutritional value for the megalopa during the desalination period. Therefore, feeding the megalopa with copepods can improve the culture performance and megalopa quality, and can also reduce the feed cost during desalination stage.