A new kind of yeast (designated as ω-yeast), produced by adding cuttlefish liver oil to the culture medium of baker's yeast
Saccharomyces cereoisiae, has been recently developed as a feed for rotifer. The rotifers cultured with ω-yeast proved to be a excellent food for marine fish larvae. But, during the mass production of rotifers with ω-yeast using large outdoor tanks, there are a few disadvantages such as the appearnace of large quantity of suspended matters and a sudden mass mortality of rotifers which is thought to be caused by the rapid change of water quality in the tanks. The present study was conducted to solve these problems, using the
Chlorella water supplement which was proved to be remarkably effective on the productivity of the rotifer with baker's yeast. The rotifers obtained in this experiment were analyzed and the food value was discussed.
Average amounts of the rotifers harvested daily/tank (40 ton) was 10.67×10
8 individuals (nearly 3.2 kg), and production with 1 g ω-yeast offered was 0.233×10
6 (0.699 g) in the tanks with
Chlorella supplement. This productivity was found to be twice higher than that without
Chlorella water (Table 2) . The average density of rotifer was maintained more than 100 individuals/m
l in the tanks with
Chlorella despite of daily 25% thinning, while, that in the tank without
Chlorella was 54-76 individuals/m
l with less frequent thinning. No marked difference in ω3 highly unsaturated fatty acid (ω3HUFA) content, which is considered to be the principal factor in the dietary value of rotifer for marine fish larvae, was found between the rotifers fed on ω-yeast alone and with supplemental
Chlorella (Table 3) . Therefore, further nutritional enrichment of the rotifer cultured with ω-yeast by
Chlorella supplement might not be expected.
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