碩士 / 國立嘉義大學 / 生物資源學系研究所 / 94 / Tai-shi costal area is one of the most important aquaculture regions of Crassostrea angulata spats. In 2003, a month’s delay of the regular massive emergence of Crassostrea angulata spats incurred barnacles to settle on spats harvesting tools, which caused serious damages to shell aquaculture. As a result, oyster farmers believe that the timing for spats harvesting should rely on the climates, the sea conditions, and the reproduction conditions of the oyster; however, no sufficient documents exist to support the argument. Liang (1981) investigated the somatic index and the setting of oysters at Bu Dai. As a result of the infrequent sampling which occurred once to twice per month, the study was unable to delineate the frequency pattern of spawning during reproduction seasons. The in-depth exploration of the cycling of the plumpness and the setting of oysters was even impossible. The current study which span from September, 2003 to November, 2004 was executed at Tai-shi costal area. The study was primarily based on investigating the cycling of the gonads of oysters and the setting of spats to explore how the setting was related to the environment during spawning seasons. The sampling took place twice per week, with a total of 68 times for the data analysis. Recorded as well were the sea temperatures, the climates, the water salinity, and the pH values of the sampling area. For each sampling, 15 to 20 grown-up oysters were collected from fixed farming shelves to measure the body weight and the weight of the wet meat, the livers, and the gonads. The somatic index, the GSI, and the HSI were calculated. Data reveal that in April the water temperatures go up abruptly and go down rapidly in September, with the months from May to August the highest and from November to January the lowest. The water salinity is high and stable during the lowest months, while it is low and unstable during the highest months. The results also show that the water temperatures and the salinity are negatively correlated (P＜0.01). The density of the spats on the harvesting tools during the high water temperature months are the lowest. The density increases gradually after August and the spawning season ends in April, with the peak occurring in October and in February. During the spawning season, the massive discharge of sperms and eggs lasts about 13 days. The setting of the spats lasts around 14 days, with the peak emerging 2 to 3 weeks after the decrease of somatic index. The barnacles cease its spawning during the low water temperature months and are obviously restrained during the high water temperature months as well. Comparing oyster shells with P.V.C board as the setting tools, it was found that oyster shells yield more spats. The high water temperature months yield the lowest quantity of spats; however, they are the months when the grown-up oysters are at their highest in somatic index and GSI. The spawning obviously decreases during the lowest water temperature months. Data further revel that the GSI value positively correlates with the somatic index (P＜0.01). The HSI value negatively correlates with the water temperatures (P＜0.05).
| Identifer | oai:union.ndltd.org:TW/094NCYU5404002 |
| Creators | 陳漢招 |
| Contributors | 鍾國仁 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
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