Ingestion, digestion and food selection of crimson snapper(Lutjanus erythopterus) larvae and juveniles

To determine the optimal feeding density of rotifer and weaning time for Lutjanus erythopterus larvae and juveniles, we studied the impact of different rotifer feeding densities on the growth, survival and food selectivity for juvenile L. erythopterus. Then we investigated the effect of weaning time 13 dph (days post hatching, W13), 16 dph (W16), 19 dph (W19) and 22 dph (W22) on the rearing performance of larval and juvenile L. erythopterus by using the evaluation indicators of growth, survival, RNA/DNA ratio and epithelial cell height of the digestive tract. The results show that the feeding density of rotifer affected the ingestion, food selection, growth and survival rate of L. erythopterus juveniles significantly. When the feeding density of rotifer was 10–20 ind·mL^–1, there was no significant difference in the growth and survival rate of the juveniles, but significantly higher than treatment groups of 1 ind·mL^–1 and 30 ind·mL^–1. In the weaning experiment, the growth and survival rates of W19 and W22 groups were significantly higher than those of the other two groups, and the W13 treatment group had the lowest RNA/DNA ratio. At 22 dph, the height of the epithelial cells of digestive tract was significantly lower in the W13 and W16 groups than in the other two groups. It is indicated that the rotifer density had significant impact on the food selectivity of L. erythopterus during mixed feeding period of rotifers and Artemia nauplii. The rotifer density of 10–20 ind·mL^–1 is recommended for the initial feeding period of L. erythopterus, and the weaning of L. erythopterus can be started on 13 dph, but the best timing was 16–22 dph.