The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


Isaschar Ben-Atia, Sigal Lutzky, William Koven, Oria Nixon, Michal Torten and Amos Tandler*

Israel Oceanographic and Limnological Research Ltd., The National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel


Larvae that ingest insufficient nutrients from hunting inappropriately-sized prey may quickly pass the "point of no return" where the digestive tract irrevocably regresses, leading to rapid mortality. In larvae of the white grouper (Epinephelus aeneus), the period between the onset of exogenous feeding and the point of no return is thought to be extremely short, stressing the importance of successful first feeding.

In light of this, the importance and duration of feeding small,homogeneously sized (<100 Ám) rotifers (Brachionus rotundiformis) vis a vis survival, population structure and ingestion rate in first feeding white grouper were tested. Two-day-old yolk sac larvae were stocked a 50 larvae/l in six 1500 l conical V-tanks with a 100% daily water exchange rate of filtered (10 Ám) sea water (25%) at 27▒1°C. After eye pigmentation and the opening of the mouth (three days after hatching), three rotifer feeding protocols were tested in duplicate tanks. The treatments differed in the duration of time that small homogeneously sized and enriched rotifers were fed to the larvae (until 5, 7 and 9 days after hatching). After these feeding periods, the larvae were fed heterogeneously sized unfiltered rotifers (ca 120 Ám) until 30 days after hatching. The survival and ingestion rate significantly (p <0.05) increased with the increasing duration of feeding filtered rotifers. This was due mainly to the markedly (p <0.05)improved survival of the smaller larvae (55 mg wet wt), which represented the most substantial segment of the population in the nine-day treatment, compared to their larger cohorts (96 and 200 mg wet wt). The improved performance of the 55 mg larvae was likely a consequence of the higher capture rate of the small rotifers shortly after the onset of exogenous feeding. These findings emphasize the critical importance of ingesting nutrients immediately following the onset of exogenous feeding in white grouper larvae.