Abstract
The ability of newly hatched larvae of Japanese Spanish mackerel Scomberomorus niphonius to resist starvation was studied in rearing experiments. Because Japanese Spanish mackerel larvae exhibit almost complete piscivory from the first feeding stage and begin to cannibalize under lack of piscine prey, they were isolated from one another during the experiments. Newly hatched larvae commenced feeding on fish prey (red sea bream Pagrus major larvae) on day 6 (after hatching) and completed yolk sac absorption by day 9 at 18.5°C. All the starved larvae had died by day 10. More than 90% of fish fed red sea bream larvae survived until day 10, whereas all fish fed rotifer (Brachionus plicatilis) had died by the same day, indicating that rotifer is useless as a prey for the survival of Japanese Spanish mackerel larvae at the first feeding stage. A clear point-of-no-return (PNR), 0-1 day of recoverable starvation, was found at the post-first feeding stage. Delayed feeding experiments demonstrated that the percentage survival on day 10 was 100% for larvae fed from day 5, 91.6% from day 6, 16.7% from day 7, 8.3% from day 8, and 0% for those fed from day 9. Fish first fed from day 7 or 8 showed significantly retarded growth during the following adequately fed period compared with fish fed from the first feeding (day 6). These results show that Japanese Spanish mackerel larvae are highly vulnerable to fasting and that the larvae's first feeding success might be critical for growth and survival in the period that follows.
