Effect of delayed initial feeding on growth and survival of Asian sea bass Lates calcarifer (Bloch) larvae

Abstract

This study investigated the influence of delayed initial feeding on growth and survival of Asian sea bass Lates calcarifer larvae under controlled conditions. Growth parameters were evaluated by assessing morphometric characteristics of the larvae. Two experiments were conducted at different initial feeding time (48 h, 72 h, 96 h and 120 h) as follows: experiment 1 was conducted to evaluate the morphometric characteristics (total length, head depth, body depth, eye diameter, gut height, musculature height, yolk and oil globule volume) under different initial feeding time. Sea bass larvae initiated first feeding at 96 h and 120 h after hatching have achieved comparatively lesser growth in total length and total weight than that of 48 h and 72 h. The morphometric characteristics of 5 DPH larvae had significant differences between 48 h and 120 h initial feeding. Similarly, significant differences were noticed between 48 h and 96 h initial feeding for all the morphometric characteristics except gut height. In 11 DPH larvae, significant differences were observed only between 48 h and 96 h for all the morphometric characteristics and it was not significant between 48 h and 72 initial feeding. It was also observed that the yolk absorption in sea bass larvae was completed by 96 h irrespective of the differences in the initial feeding. Similarly, oil globule was completely utilized at 120 h after hatching. There was no significant difference in the yolk volume and oil globule utilization of 1 DPH and 2 DPH larvae among different treatments. The yolk volume of 3 DPH larvae initiated first feeding at 48 h (0.0122 ± 0.0008 mm 3) and 72 h (0.0110 ± 0.0008 mm 3) had significant differences with yolk volume of larvae initiated first feeding at 96 h (0.0098 ± 0.0006 mm 3) and 120 h (0.0096 ± 0.0003 mm 3). However, the oil globule of 4 DPH did not vary significantly between the treatments. Experiment 2 was carried out to find out the impact of delayed initial feeding on the survival rate. Sea bass larvae were initiated first feeding at 48 h, 72 h, 96 h and 120 h under different treatments and after 21 days rearing, survival rate was estimated. Survival rate was higher when the sea bass larvae initiated initial feeding at 48 h (31.46%) when compared to 72 h (21.18%) and 96 h (8.42%). Complete mortality was recorded on 9 DPH for the larvae initiated first feeding at 120 h. Significant differences were observed between the treatments. The present study suggests that the first feeding of sea bass larvae must be initiated at 48 h for yielding better growth and survival.