| 英文摘要 |
The first part of this study mainly focuses on how climate change affects the Bigeye tuna in the Pacific Ocean. In order to discuss long-term and meso-scale climate changes influence the BET variation, we separate the operation type of longline into two types, Deep longliner (DLL) and regular longliner (RLL), and divide the fishing grounds into four areas (AR) by cluster analysis using catch composition data, then conduct GLM method to observe CPUE variation. In long-term of climate regime shift, both DLL and RLL move to eastern area in 1977 which SST anomalies had higher temperature. After this year, the CPUE gravity of longitude had similar trend with PDO. In warm phase, the gravity leans to the east and to the west in cool phase. Compared to the gravity in latitude, before 1977, the CPUE distribute leans to north; and lean to south after 1977, than came to north again in 1989. These timing are similar with climate regime shift. In meso-scale of ENSO period, we mainly focus on the relationship between net primary production and BET CPUE. NPP has significant relationship on BET variations (P The second part of this study is on yellowfin tuna, one of the major targets of tuna longline fishery in the Arabian Sea. We collected the longliners data caught between 10￠XN~25￠XN and 45￠XE~75￠XE by Taiwan longline fleet and environment variables such as Sea surface temperature (SST), sea temperature (5~460m), chlorophyll-a concentration and thermocline depth during the period of 1998 to 2006 for analysis. Principle components analysis (PCA) used to investigate the relationship between the fishing condition and the oceanic environmental factors. The catch per unit effort(CPUE) was calculated as the number of fish caught by 1000 hooks in 5￠X!N5￠X degree square grid and showed that the fishing season began from February to July, the averaged CPUE was 13.21 (inds/1000 hooks) and the highest value of mean about 19.16 (inds/1000 hooks) in April and May. The result of PCA shows monthly evolution of CPUE and oceanic condition of the Arabian Sea. For CPUE, the sub-surface temperature, sub-surface salinity, chlorophyll-a concentration were significant. During the high CPUE period the sub-surface temperature between 105~205 m was 17~24￠XC. The significant of 2 month lag of chlorophyll-a concentration with CPUE suggested that the forage concentration was the attracted factors to accumulate the tuna school. The results also shows the reasons cause the high catch and high CPUE throughout 2005 whole year because of the increase of the vertical sea temperature and slinity in the Arab |
