Wullur, Stenly and Sakakura , Yoshitaka and Hagiwara, Atsushi
(2007)
Feeding, growth and survival of seven-band grouper larvae fed with two-minute rotifer Proales similis and SS-type Brachionus plicatilis.
Proceeding of Joint International Symposium on Marine Science and Technology.
Abstract
Mouth size of early life stage of seven-band grouper ranges between 180-220 µm and is quite small among fish larvae. At first feeding, when fed with the sizes of rotifer Brachionus plicatilis sp. complex, the larvae tend to select smaller sizes of the Brachionus. Since lorica sizes of the Brachionus are in the range of 90-340 µm, the effect of live food whose size is smaller than the Brachionus need to be examined. In this experiment, rotifer Proales similis (60-100 µm) was fed to the larvae and the effects on feeding, growth and survival were compared to those fed SS-type B. plicatilis.
Nine polycarbonate tanks in capacity of 100 liters were prepared following Ruttanapornvareesakul et al. (2007). At first feeding (4 DAH), 3 dietary treatments of P. similis at 20 ind./mL, SS-type at 20 ind./mL and mixed rotifers at 20 ind./mL (consisted of 10 ind./mL of each rotifer) were fed to the larvae of seven-band grouper for 10 days after hatching. Sampling was made on 4, 5, 6, 8 and 10 DAH by taking around 25 larvae from each tank for the analysis of feeding and growth. On 10 DAH, all surviving larvae were harvested and survival rate and dry weight were obtained
By dissecting gut content of the larvae that were sampled on 4 DAH, it was found that 100% of the larvae ingested both rotifer species. On the first three days of feeding however, the larvae in the dietary treatments containing P. similis showed a significantly high feeding amount compared to the larvae fed with SS-type alone. It is suggested that the smaller size of P. similis has facilitated the larvae to attain their high feeding amount. By comparing selection of the larvae to each rotifer species in the treatments of mixed rotifers, significantly high selection of P. similis was detected on 4 DAH although the selection was then shifted to SS-type on 6-10 DAH. This result demonstrated that th larvae of seven band grouper prefer to SS-type on first days of feeding although the larvae have ability in ingesting both rotifer species. Of the three dietary treatments, seven-band grouper larvae showed significantly faster growth till 6 DAH when they were with mixed rotifers compared to those fed P. similis or SS-type alone. It is suggested that the higher feeding amount of the larvae in this treatment have influenced the faster growth of the larvae. The larvae in the treatment of mixed rotifers also showed higher survival as well as total yield (number of survival larva X individual dry weight) at the end of the experiment
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