碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 98 / The operation of Taiwanese offshore longliners with large vessel number and various fishing types has expanded over the Pacific, Atlantic, and Indian Oceans due to increasing fishing capacity. As most of the offshore longliners are subsistence fishery, it is always difficult to collect their fishing logbook data and therefore related studies are lack. In order to explore the information of their fishing capacity, species composition and spatio-temporal distribution characteristics, we analyzed fishing data of the offshore longline fishery during 2003-2007 collected and compiled by the Overseas Fisheries Development Council of the Republic of China, associated with surface sea temperature (SST) and sea surface color (SSC) data downloaded from the web site of NASA. The results were showed as follow:
1.About the hook number deployed per day per vessel in different level of Gross Registered (GRT) Ton levels, there are 400-500 hooks (>55%) for CT1, 500-700 hooks (>62%) for CT2, 600-1500 hooks (about 90%) for CT3, and 1200-1600 hooks (>65%) for CT4.
2.In regard to the spatial distribution of fishing sites, only vessels of CT1 were limited in the coastal waters.Those for CT2 has expanded to the Indian and western Pacific Oceans, and vessels over CT3 covered throughout the Pacific, Atlantic, and Indian Oceans.
3.The main target species for Regions 1 and 2 (WCPFC’s system) were mostly yellowfin and bigeye tunas (>90%), and albacore were for Regions 4~6 (>80%). About 39% and 24% fishing effort were allocated in Regions 1 and 3, respectively. The highest concentration of fishing effort were mainly located in the areas centered in Guam, west to Micronesia and south to Palau, as well as the areas south of Equator and east to Solomon Islands.
4.We used Generalized Linear Model to select effective factors for tuna CPUE and found that the factors varied by species which including GRT, Region, SST, SSC, by catches and etc. For yellowfin tunas, the major target, the most important factors were GRT, Region and SSC. However, for bigeye and albacore tunas no particular effective factors. Only the effect from Region were noticeable for albacore and catch of surface species (yellowfin and billfish) have deep influence on CPUE of bigeye tuna.
We affirmed that the offshore longline fishing data is an indispensible part as we found that its fishing ground and catch composition differed greatly from those for large longliners, especially in northwest Pacific Ocean (Regions II and III). To apply sooner the offshore fishing data in tuna stock assessment, it is very important to improve current data collection scheme and management measures
| Identifer | oai:union.ndltd.org:TW/098NTOU5451023 |
| Date | January 2010 |
| Creators | Mei-Yen Lee, 李美燕 |
| Contributors | Hsueh-Jung Lu, 呂學榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 79 |
Page generated in 0.0016 seconds