The percoid fish, Oplegnathus fasciatus (Temminck and Schlegel), is one of the most important marine fish currently cultured in southern Japan. Therefore the mass production of juveniles of this species has been the subject of great.
The rotifer Brachionus plicatilis fed on Chlorella sp. or on a combination feed composed of Chlorella and bakers' yeast has been shown to be a effective diet for the larvae than that composed of only bakers' yeast. The reason for the difference in food value is considered to be due to the eicosapentanoic acid (20:5ω3) content of Chlorella. E. acid is an essential fatty acid for growth and survival in larvae and juveniles of several marine fishes such as red seabream Pagrus major, black porgy Acanthopagrus schlegeli, and others. However, in rainy or high temperature periods, mass production of Chlorella is sometimes unsuccessful. At these times, the bakers' yeast rotifer is often enriched with a small amount of Chlorella in an attempt to provide an adequate diet for the larvae.
The presnt studies were conducted to examine the possibilities of rearing the larvae without Chlorella, using a special yeast in which fat and oil were partially assimilated. As a first step, the nutritional effect of enriching the bakers' yeast rotifer with the special yeast was ascertained by mass rearing the larvae in a 100 ton tank (60 thousand juveniles of 20mm in total length were obtained). Secondly, mass production of rotifer with the special yeast was found to be possible using the same method as bakers' yeast rotifer. The average production of rotifers per 1g feeding of the yeast was 102 thousand individuals (0.306g). Finally, the high nutritional value of the yeast-rotifer to the larvae was proved by the mass production of juveniles in a 200 ton tank (220 thousand juveniles of 25mm in TL were obtained).