碩士 / 國立高雄海洋科技大學 / 漁業生產與管理研究所 / 106 / This study was based on observers’ records of the Taiwanese tuna longline fishing fleets operating in the Atlantic Ocean in the period 2004-2015. Observers’ data analysis included those of operation area, fishing effort, species composition, shark by-catch species composition, shark discard/release rates, and catch per unit effort (CPUE) of blue shark from Atlantic Ocean. Five areas: A (north of 20°N), B (5°N-20°N), C (5°N-15°S), D (15°S-50°S, west to 20°W) and E (15°S-50°S, 20°W-20°E) were categorized based on the blue shark nominal CPUE distribution. To cope with the high zero shark catch percentage, the CPUE of blue shark, calculated as the number of fish caught per 1,000 hooks, was standardized using a two-step delta-lognormal approach that treats the proportion of positive sets and the CPUE of positive catches separately. Standardized indices with 95% bootstrapping confidence intervals were reported. Major shark by-catch species were blue shark (Prionace glauca) (75.74%), bigeye thresher shark (Alopias superciliosus) (8.91%), shortfin mako (Isurus oxyrinchus) (4.53%) in the North Atlantic Ocean and blue shark (67.70%), crocodile shark (Pseudocarcharias kamoharai) (14.38%), cookiecutter shark (Isistius brasiliensis) (5.68%) in the South Atlantic Ocean. The standardized CPUE showed a stable trend for blue sharks from 2007 to 2014. The results obtained in this study can be improved if longer time series observers' data are available.
| Identifer | oai:union.ndltd.org:TW/106NKIM0451001 |
| Date | January 2018 |
| Creators | CHEN, PO-WEN, 陳柏妏 |
| Contributors | TSAI, WEN-PEI, 蔡文沛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 83 |
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