博士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 97 / The whale shark Rhincodon typus is the largest fish in the world. Its biological, ecological, and ethological studies are limited. From 2001 to 2008, mean annual catches of set nets from southwestern Taiwan were higher than that from northwestern and northeastern Taiwan. In addition, mean total length (TL) of whale sharks caught from June to October was smaller than the ones caught from November to May. Whale sharks caught in deeper ocean are larger. Sex ratio (male/female) shows that more males are caught around Taiwan waters.
Nine individuals (3.8-9.6 m TL) were tagged and released with SPOT or PAT tags. Data from electronic tags fit to sea surface temperatures, thermal fronts, ocean colors, bathymetric topography images, and typhoons trail information, indicated that whale sharks migrated and moved for feeding. The whale shark moves mainly in the regions 50-150 m below sea surface, and in temperatures 15-32 °C. Additionally, in summer and fall, the whale shark stays longer in deep ocean in daytime, and ascends in nighttime, especially from midnight to dawn. In winter and spring, the whale shark surfaces frequently in both day and night. Migratory routes show that whale sharks usually swam to open ocean in summer and fall, and move to north-south coasts in East Asian continental shelf regions in winter and spring.
In the studies regarding whale sharks’ age and growth, there were vertebrae from 92 whale sharks investigated. Additional vertebrae from 2 full-term embryos which were 61.0 cm TL female and 54.8 cm TL male, from a pregnant female caught in 1995, were also used. Maginal increment ratio and centra edg analysis result biannual growth rings formation. Data of 94 vertebrae and an additional published 64-cm-TL data of the biggest embryo were fitted to three parameters von Bertelanffy growth equation (VBGE). The parameters for VBGE were estimated to be L∞=16.31 m TL, k=0.037 year-1, and t0=-1.24 years for both sexes. Ages at maturity back-calculated from VBGE were estimated to be 17.2 years for male and 19.2-22.6 years for female. Maximum longevity is estimated to be more than 79 years, and average annual growth rate over the whale shark’s life span is 19.8 cm/year, suggest this shark is a very slow growth species. In addition, the Northwest Pacific population probably migrates to Taiwan waters when they are 3-14 years old.
| Identifer | oai:union.ndltd.org:TW/097NTOU5451020 |
| Date | January 2009 |
| Creators | Hua Hsun HSU, 徐華遜 |
| Contributors | Shoou Jeng JOUNG, 莊守正 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 177 |
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