Study on the relationship between temperature-depth and distribution of tunas and billfishes in the tropical Indian Ocean

• Main Authors: Wang, Chung-Ying, 王鐘瑩
• Other Authors: Hsu, Chien-Chung
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/70507233810679961057

碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 98 === This study is sponsored as a project by FA.COA (Fisheries Agency, Council of Agriculture, Executive Yuan, R. O. C.) during July and December in 2007, and cooperates with longline-fishing industry. In order to collect the temperature and depth in water layers and to record the gains of fish, there are minilogs on the branchlines of two longline -fishing boats in the Indian Ocean. By recording the relationship between temperatures, depth of different hooks, and the fish catch, this study discusses the inhabitable temperature-depth range , and the situation of vertical distribution of tunas and billfishes in the Indian Ocean. The result shows the gains of fish of Boat 1 and Boat 2 are Thunnus obesus(11652), Thunnus albacares(2155), Istiophorus platypterus(1167), Xiphias gladius(717) and others (1654) in ordered; the accumulated records of temperature (1092), depth (696). The CPUE of hooks of Thunnus obesus is much higher in deep layer, and the CPUE of Thunnus albacares, Istiophorus platypterus, and Xiphias gladius is higher in the surface layer. Besides, there is a trend the hooks increase as the temperature goes lower and the layer goes deeper. Due to the similarity of main fishing temperature and depth between two boats, this research analyzes them together. And the result shows the average temperature and depth for Thunnus obesus are 12.8~16.8℃ and 155.5~212.3m; Thunnus albacares, 14.9~20.5℃ and 115.1~185.5m；Istiophorus platypterus, 16.8~25.4℃ and 68.8~183.4m; Xiphias gladius, 11.7~23.5℃ and 130.0 ~ 187.0m.