Determination of appropriate feeding schedules from diel feeding rhythms in finfish larviculture

Abstract In finfish larviculture, feeding regimes and schedules vary with hatchery and species. They have no biological or technological foundation and are dependent of operator expediency and previous experience. Inadequate feeding regimes and/or inappropriate food intake, especially during early larval stages, may result in a decline in health and/or quality and high mortalities. Fish have species-specific diel feeding rhythms; therefore, feeding schedules in larviculture cannot be determined uniformly among target species. To improve survival and quality, it is important to establish feeding schedules corresponding to the diel feeding rhythms of larval fish species. In fish, the feeding and circadian rhythms are linked; most species have diurnal feeding peaks, especially at dusk and dawn, such as flat fishes, groupers, sparids, devil stinger Inimicus japonicas and ayu Plecoglossus altivelis . These fish do not ingest food at night and the larvae actively feed at dawn and dusk. Differences in this trend have not been reported during the co-feeding period of rotifer and Artemia nauplii. Although ocellate puffer larvae also have diurnal peaks of food intake, they commenced ingestion before day break. The delay in first feeding causes serious problems in finfish larviculture and in many cases, it is performed to prevent this delay. After mouth opening, larvae do not have a well-developed functional jaw and, thus, rotifers or Artemia nauplii remain in the rearing water. They metabolize the enriched nutriments, resulting in deterioration in the nutritional quality of the residual live food. Therefore, the timing of first feeding is important. In conclusion, the feeding schedule of a particular fish species should be determined on active diel ingestion. Delays in active ingestion result in un-ingested live food remaining in the rearing water and consequent nutritional deterioration. Therefore, feeding schedules in finfish larvae and juveniles should be matched to the peak of food intake.