Effects of temperature and delayed initial feeding on the growth of Malabar grouper (Epinephelus malabaricus) larvae

This study investigated the impact of delayed initial feeding on the growth and survival of early stage Malabar grouper Epinephelus malabaricus larvae in relation to the absorption of endogenous reserves under different temperature conditions. Two experiments were conducted as follows: experiment 1 was conducted to examine the process of yolk and oil globule absorption in the larvae during endogenous feeding at three different temperatures (25, 28, and 31 °C). Mean volume of yolk sac for 25 °C (25.2 ± 0.58) was significantly larger than for 28 °C (28.1 ± 0.15) and 31 °C (31.0 ± 0.25) at larval onset of mouth opening and at onset of feeding, with the absorption of yolk sac and oil globule having a tendency to be consumed more rapidly with increasing temperature.Experiment 2 was carried out to investigate the effect of delayed initial feeding on the subsequent growth and survival at five different feeding regimes at 28 °C. The larvae were fed a small S-type of Thai strain rotifers at a density of 20 ind./ml except for Group 5 (Gp. 5). Gp. 1: rotifers fed initially from the onset of mouth opening, Gp. 2: rotifers fed initially from 6 h after mouth opening (HAMO), Gp. 3: rotifers fed initially from 12 HAMO, Gp. 4: rotifers fed initially from 24 HAMO, and Gp. 5: starved control. Larval growth showed significant differences between Gp. 1–3 and Gp. 4–5 at the end of the experiment, 96 HAMO (P < 0.05). In contrast, starved larvae (Gp. 5) showed the negative growth from 24 to 96 HAMO. The beginning of negative growth point coincided with the time of complete oil globule absorption at 28 °C. These results indicate that larval growth was closely related with endogenous reserves, and larvae possess a very short period during which they are resistant to food deprivation. We conclude that their growth was affected if they fail to initially feed within 24 HAMO at 28 °C.