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|Title: ||Distribution of bigeye tuna (Thunnus obesus) in relation to variability of net primary production in the Pacific Ocean|
|Authors: ||Yi-Hui CAI;I-Hsun Ni;Hsueh-Jung Lu|
|Contributors: ||NTOU:Department of Environmental Biology and Fisheries Science|
|Issue Date: ||2011-10-20T08:24:28Z
|Publisher: ||The 4th International Symposium on FISH-GIS/Spatial Analyses in De Niro, Brazil|
|Abstract: ||abstract:The catch per unit effort (CPUE) and spatial distribution of bigeye tuna (BET) caught by Taiwanese longline varied annually, which is particularly significant in the Equatorial region during El Niño period. Basin-scale variability of sea surface temperature (SST) and chlorophyll a (chl-a) are two major ocean surface factors that often used to describe habitat range or even to locate tuna fishing ground of tunas. However, for BET in correlations with temporal average of SST, chl-a and CPUE are always poor due to complexity of ocean process and fish behaviors. In this study, we use Eppley-vertically Generalized Production Model (VGPM), a “chlorophyll-based” algorithm incorporated factors of surface chl-a, surface irradiance, SST and day length, to compute net primary production (NPP) values. Fishing efforts from September 1997 to December 2005 were separated into Deep Longliner (DLL) and Regular Longliner (RLL) by hooks per basket (HPB): if HPB≦12 named RLL whereas HPB≧13 named DLL. Then we matched the monthly maps of NPP and BET CPUE, and found that the BET CPUE of DLL in number (N/1000hooks) was significantly restrained in high NPP area where CPUE in weight (Kg/1000 hooks) were much higher than RLL’s. BET CPUE of RLL was mostly located in areas surrounding lower NPP area, with little exception in the high NPP area. The movement of the high NPP area can result in significant shift of BET CPUE in both DLL and RLL, especially during El Niño and La Niña periods. Therefore, the variability of net primary production is an explainable variable to explain variability of BET CPUE distribution in the Pacific Ocean. However, during the El Niño and La Niña periods the fluctuations of BET CPUE were more than NPP’s effects. We also analyze the subsurface water temperature data (include MLD) to discuss the physical effect of vertical structure on BET’s spatial distribution.|
|Appears in Collections:||[環境生物與漁業科學學系] 演講及研討會|
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