| 英文摘要 |
??Observers’ data analysis including operation area, fishing effort, species composition, shark by-catch species composition, catch per unit effort by species, seasonal variation of CPUE in blue shark from Atlantic Ocean were presented. For the purpose of analyze the CPUE trend of blue shark, the observers’ records of Taiwanese tuna longline fishing vessels operating in the Pacific Ocean and India Ocean from 2002-2008 were analyzed firstly. According to shark catch rate, four areas namely, A (0o-20oS), B (south of 20oS), C (0o-20oN), and D (north of 20oN), were categorized in the Pacific Ocean.The Indian Ocean was stratified as 4 areas namely, I (10oS-25oS), II (south to 20oS, 20oW-150oE), III (10oS-10oN) and IV(10oN-30oN). The shark catch data reported by observers were used to adjust the historical shark catch in Task I and to estimate blue shark and mako shark or silky shark catches for Taiwanese longline fishery in the Pacific Ocean and Indian Ocean. In Pacific, the shark bycatch in tropical area (areas A and C), is higher than that in temperate area (areas B and D). In India Ocean, the high shark bycatch rate was found in major fishing ground for the yellowfin and albacore tuna fleet (areas I and IV). Shark bycatch in weight was estimated about 10 thousand tons between 2001 and 2008 in Pacific Ocean and Indian Ocean. Standardized CPUE and relative CPUE series of major bycatch sharks caught by Taiwanese longline fishery showed a stable trend. The stable trend suggested that the blue shark, mako shark and silky shark stock in the Pacific and Indian Ocean seems at the level of optimum utilization. The results in this study are preliminary and further investigation is needed. |