Fishing efficiency of the Taiwanese offshore tuna longlining fishery

• Main Authors: Ling Huang, 黃淩
• Other Authors: IH NI
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/34274418910979397941

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 93 === Abstract The conservation consciousness of the international fishery resources have been gradually increased in recent years, especially to the commercial important migratory fish species in the high seas such as tuna and tuna-like species. Several regional international fisheries organizations have been formed to manage them with catch quota based upon stock abundance in international waters. Consequently, it makes the necessity of having reliable catch statistics for the offshore tuna longlining fishery, particularly based upon Taiwanese fishing harbors. Entrusting with the sampling vessels to verify the catch statistic would be the bargaining counter in international fisheries organization meetings in future. Furthermore, the current catch data reported by fishers could not often represent the real fishery situation. Therefore, it is very important and great urgency to understand the real fishing operation if we can have some assigned sampling fishing vessels with designed catch statistics so as to compare with current reporting system. Thus, we selected 42 sample vessels with questionnaire from three main longlining fishing harbors that are NanFanAo, DongGang, SinGang during 29 November 1998 to 15 June 2003. Reported catch data were analyzed as follows: (1) fishing efficiency of sampling vessels among three fishing ports; (2) fishing efficiency in relation to sampling vessel tonnages; (3) fishing efficiency between day and nighttime settings; (4) fishing efficiency among using different baits; (5) fishing efficiency among four seasons; and (6) correlation between sampling vessel tonnages and longest fishing distance. It revealed that the fishing sites are significant different among three fishing ports, the fishing vessels from NanFanAo and SinGang catch mainly the non-target dolphinfish. The DongGang longliners caught mainly target species such as yellowfin tuna. The catch rate of the target species decreased with vessels tonnage, but increased with average fish weight. Also, large longlining vessels caught mainly the target species. The catch rate was higher during the nighttime setting than daytime. However, there was no significant difference of the catch rate between the day and nighttime setting for target species, but significant difference for non-target species. Among fishing baits, he moonfish was the best to catch both the target and non-target species. The fishing grounds were varied significantly in four seasons. The eastern waters off Taiwan were the fishing ground during spring and summer, longlining was then transferred to the South China Sea during autumn and winter. There is a positive correlation between vessel tonnages and the longest distance of fishing. Therefore, it might be possible to replace CPUE by catch per day instead of catch per thousand hooks for current calculating tuna stock abundance estimation. Key words：Taiwan offshore, tunas, longlining, fishing efficiency, fishing ports, vessel tonnages, day and night setting, baits, seasons.