碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 105 / Sailfish and spearfish are widely distributed in the Atlantic Ocean. Catch records of these two species were combined due to as non-target species in the Taiwanese tuna longline fishery in the Atlantic Ocean. However, there is a need to separate catch data of sailfish and spearfish into two species for assessment of Atlantic sailfish. Logbook data of the Taiwanese tuna longline fishery were collected in this study from 2009 to 2015, including year, month, attitude, longitude, fishing effort and catch of sailfish. We compared various methods to estimate catch ratios of sailfish in this fishery and different approaches to standardize CPUE (Catch per unit of effort) for the species, in order to develop an abundance index of Atlantic sailfish for 1968-2015. Results showed that GAMs (Generalized Additive Models) are the most appropriate methods used to estimate the catch ratio of sailfish in the fishery and that the delta-lognormal approach can deal well with large amount of zero catch data for sailfish. Standardized CPUE showed that sailfish abundance substantially decreased from the late 1960s to the 1970s and remained relatively stable thereafter. Given that the Atlantic sailfish might be overfished and large uncertainty in the assessment results, long-term series of abundance index should be developed to be used as basic input data for stock assessment to understand current stock status and the variation. Results from this study could be used to provide scientific-based suggestions for fishery management.
| Identifer | oai:union.ndltd.org:TW/105NTOU5451022 |
| Date | January 2017 |
| Creators | Tai, Ching-Hsuan, 戴靖萱 |
| Contributors | Su, Nan-Jay, 蘇楠傑 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 90 |
Page generated in 0.0016 seconds