碩士 / 國立臺灣海洋大學 / 水產養殖學系 / 94 / This research was carried out to design adequate processes in a simple recirculation system to rear the larvae/fingerlings (from 3 to 9 cm) of king grouper (Epinephelus lanceolatus), in order to make a Standard Operation Procedure (SOP). The SOP includes healthy larvae choosing, system sterilization, management of fish rearing, feed and water quality management, and diseases prophylaxis. As a second point, we use this culture system to rear larvae/fingerlings, and thus to discuss the effect of different treatments with controlled temp (30℃), room temp (27∼30℃), and the reduction of salinity when the fingerlings of grouper get infected with virus. The expected output is the increase in the survival rate during the larvae (2 cm) to fingerling (9 cm) phase. Before the experiments, all the larvae/fingerlings were tested with PCR and Nested-PCR to make sure they were free of Taiwan Grouper Iridovirus (TGIV) and Nervous Necrosis Virus (NNV).
Experiment 1: Two fiberglass tanks (2 tons) were used. The A tank was stocked with 5000 white-body larvae (1.5∼2.5 cm), the B tank was stocked with 3000 fingerlings (3 cm), the fish came from different hatcheries. The tanks were setup with a simple recirculation system, and the fish were fed with artificial feed (crude protein 50%, crude lipid 8%). During all the experimental period, the rearing/culture was handled with the SOP being in the developing stage in this laboratory. At the end of the experiment, the fish in the tank grew till 7 cm and the fish in the tank B grew till 9.9 cm respectively with survival higher than 95%.
Experiment 2: During this experiment, the nursery process/fish culture followed the SOP that was developed by the previous experiment, in order to confirm the practicability of this SOP. TGIV and NNV outbreaks were present when the fish had 5 cm in both the treatments with controlled at 30℃ and room temperature (27-30℃). After 30 days, high mortality rates were observed (93% and 93.7% of 3000 larvae). The results show that constantly controlled temp at 30℃ cannot reduce mortality induced by NNV and TGIV. Furthermore, during the virus outbreak orange-spot grouper (E. coioides) (12 cm) were reared in the same tanks but with 0% mortality. Apparently, it seems that this size orange-spot grouper has a better immunity against NNV and TGIV than the king grouper.
Experiment 3：3000 white-body larvae were reared in the system. After 2 weeks, high quantity of NNV and TGIV were observed by means of PCR. Following this, the salinity in the A tank was reduced from 34 ppt to 6-8 ppt in 3 days time, and in the case of the tank B, the same treatment but in a time of 6 days later. The survival after 30 days were 74% for tank A, and 48% for tank B respectively. As a final stage, challenge tests were carried out with the recovered fingerlings. The fish were injected with TGIV or NNV and then reared in 5, 15, 25 and 34 ppt seawater or in seawater initially then decreased to 5, 15, 25 and 34 ppt seawater, respectively. The cumulative mortality caused by virus infection in these virus-challenged fish was in all cases 0%. This result shows that the low salinity treatment decrease the mortality caused by NNV and TGIV, and in addition, the recovered fingerlings had acquired immunity.
As a conclusion, it was observed that the precise administration of the SOP is very helpful to increase the survival and to induce the fish to accept artificial feed when rearing larvae/fingerlings of king grouper. When having the virus outbreak, there were no means to control the temp (30℃), but the reduction of salinity and the correct application of the SOP in conjunction with good management showed that the outbreak can be inhibited. However, further research is needed to identify the mechanism of reducing salinity on inhibition of which virus outbreak
| Identifer | oai:union.ndltd.org:TW/094NTOU5086034 |
| Date | January 2006 |
| Creators | Jeng-Baang Chen, 陳政榜 |
| Contributors | Chyng-Hwa Liou, 劉擎華 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 161 |
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