碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 103 / Bigeye tuna (Thunnus obesus) is one of the important commercial species for longline fisheries in Atlantic Ocean. In this study, we collected the logbooks of the Taiwanese longline fleets and marine environmental data, including sea surface temperature (SST), mixed layer depth (MLD), depth of 20-degree isotherm (D20), sea surface height anomaly (SSHA), and sea surface salinity (SSS) of the Atlantic Ocean during the period of 1981 to 2009. This generalized additive models (GAMs) were used to investigate the relationships between environmental variables and catch rates for evaluating the fishing condition of bigeye tuna in the Atlantic Ocean.
The model selection processes showed the cumulative deviances explained by the selected GAMs were 60.7% and 61.3% in the entire Atlantic Ocean, and the tropical region, respectively. Spatial terms (longitude and longitude) accounted for a large part of the variations in the tropical Atlantic Ocean, and SST and D20 contributed substantially to explained deviance. The SST was 24~28℃ and D20 was 50~150m during the high CPUE period. The high catch rates of bigeye tuna was also influenced by MLD ranging from 40 to 70m, SSHA ranging from -0.1 to 0.05m, and SSS ranging from 35.4 to 37.2psu.
The catch rates and distribution of bigeye tuna in the Atlantic Ocean were sensitive to climatic and environmental variation. The predicted relative abundance reveals a notable increase in the tropical Atlantic Ocean during positive tropical northern Atlantic (TNA) events, and is related to the higher SST and D20 in the tropical Atlantic Ocean. The time-series trends in the annual predicted relative abundance of bigeye tuna exhibited a high correspondence with the annual TNA. Decadal-scale variability was found for bigeye tuna with significant shifts occurring around 1995 which was in accordance with TNA.
| Identifer | oai:union.ndltd.org:TW/103NTOU5451025 |
| Date | January 2015 |
| Creators | Chou, Chin-Pei, 周芹沛 |
| Contributors | Lee, Ming-Anne, Lan, Kuo-Wei, 李明安, 藍國瑋 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 65 |
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