Using Remote Sensing and Catch Data to Detect Ocean Hot Spots for Skipjacks in the Western Central Pacific Ocean

本研究以我國鰹鮪圍網之漁獲資料及遙測資料進行分析，藉以了解中西太平洋近年來漁獲正鰹之海洋環境條件及其變化。採用的方法為將日別漁獲資料，依所填報之群性進行1度方格網格化之處理，再與同範圍內1度方格表水溫及葉綠素濃度整合，並計算其棲地適合度指標及定義熱區範圍，探討正鰹分佈熱區之海洋環境指標。主要研究結果顯示，在漁場經度重心方面，以素群之移動較為劇烈，受到聖嬰南方震盪現象影響時，年間變動最明顯。以漁獲位置之SST及Chl-a計算棲地適合度指標在50-100%範圍，即SST在29.6-30.4°C且Chl-a在0.04-0.12 mg/m^3，可定義為正鰹偏好水域。此範圍雖不因群性而異，但東西向移動情形劇烈，且與正鰹月別平均漁獲率之分佈移動具一致性。比較SST及Chl-a兩因子計算HI預測熱區之結果顯示，單因子方面，SST為影響正鰹分佈之主要因素，預測正確性較Chl-a高，雙因子則約可提高預測正確性1倍。

關鍵字

中西太平洋；聖嬰南方振盪；正鰹；群性；熱區

並列摘要

In this study, we analyzed catch and effort data of Taiwan tuna purse seines fishery and corresponding remote sensing data in the Western Central Pacific Ocean to understand the preferable oceanic conditions for skipjack habitat as well as their variability. The daily catch and effort data of three school types (free, log and FAD) were aggregated monthly into 1 by 1 degree and matched with SST and Chlorophyll-a (Chl-a) data. The Habitat Suitability Indices (HSI), defined as probability (%) of oceanic factors located in highest interval, was developed to defined hot spots area for skipjacks in the WCPO. The major results of the analysis are as follows: The El Niño Southern Oscillation events strongly affect both oceanic conditions and spatial distribution of skipjack in the equatorial Pacific. Among the three school types, the migration range of free school was the widest. The highest HSI value corresponded significantly with the areas of high probability index of environments, suggesting that the specific ranges of both SST and surface Chl-a provide reasonable indicators for detection and visualization of skipjack hot spots. According to frequency distribution of SST and Chl-a corresponding to fishing locations during 1998-2007, the HSI range of 50~100%, i.e. 29.6-30.4°C for SST and 0.04-0.12 mg/m^3 for Chl-a could be defined as preference waters for skipjack. Ranges of preferential waters were without differences among school types; however, zonal displacement performance was significant and synchronized with the displacement of catch rates. When compared the validity rates of the hot spots area predicted by suitability indices based on SST were higher than those based on Chl-a. In addition, HSI based on both SST and Chl-a could double the validity rates that a single factor have.

並列關鍵字

WCPO ； ENSO ； Skipjack ； School type ； Hot spots

國際替代計量

Using Remote Sensing and Catch Data to Detect Ocean Hot Spots for Skipjacks in the Western Central Pacific Ocean

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