| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 96 === The grouper, which is the most valuable fish, has been very popular all over the world, especially in Asia. In order to improve the aquaculture technology for different groupers, the purpose of this work is to study the fingerling rearing techniques of tiger grouper Epinephelus fuscoguttatus, especially focusing on cannibalistic problems, the most suitable feeding frequency and stocking density. An indoor recirculation system was adopted as the experimental environment in this study. The water and instruments were disinfected, as well as offering good-quality feed, so as to reduce the influences of virus and other harmful factors. The results of rearing experiments reveal that the highest survival rate was 91%, and that the main reason of death was cannibalism. Besides, there was no disease in this process because we always kept a high-quality rearing environment and took care of everything from the very beginning. In order to reduce the death toll of fingerlings because of cannibalism, we have to understand the relationship between the cannibalistic problem and the body-size difference. According to the results of this study, the relationship between the cannibal and prey could form an equation: TL(prey) = 0.68TL(canni) + 5.36. Based on this equation, we could realize that the cannibalistic problem will occur most frequently when the body-size difference reaches 1.13-1.33 times. Thus, this equation could be used to predict the possibility of cannibalistic problems, and could help the fish-keeper determine when to separate different body-size tiger groupers. In the other experiment, we focused on the most suitable feeding frequency and stocking density. Based on the results, we concluded that the best feeding frequency is 6 times per day, and the best stocking density is 30-50 fishes/L. Interestingly, groupers tended to be territorial, easily frightened and not appetitive in lower stocking density (5 fishes/L). We therefore suggest that high stocking density might be beneficial for tiger groupers’ fingerling rearing.
In conclusion, it’s of importance for grouper-keepers to maintain high-quality rearing environment in order to reduce the risk of the disease and virus-infection. Additionally, it might also be beneficial to moderately increase the feeding frequency and stocking density during the fingerling rearing process. If the body-size difference exceeded the threshold of cannibalism, classifying and separating different body-size fishes is one of effective approaches to reduce the cannibalism.
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