東海南部大陸棚鎖管捕捉量與臺灣東北部湧升流區變動的關係及動力機制研究

本研究探討臺灣東北海域湧升流區與東海南部大陸棚海域鎖管資源量年變化的物理海洋原因和背後的動力過程。研究中使用佈放於臺灣東北海域之彭佳嶼溫壓站資料，配合衛星影像資料、氣象資料及鎖管捕捉量等資料，以資料相關分析和海洋動力理論為基礎，探討臺灣東部黑潮主流的變動、東北海域湧升流區水溫及水位變動、季風變化、臺灣海峽北向流、冬季中國大陸沿岸南向流、北太平洋西行中尺度渦旋等動力過程的互制和影響鎖管資源量之關係。研究結果顯示，在年際變化上鎖管的資源量與彭佳嶼水溫(資源量資料的前一年10月及同年4月)有正相關性，由於鎖管主要會在每年的3−5月與10−12月洄游至湧升流區附近海域繁殖產卵，通常較高的水溫有助於幼體發育，進而可以提高鎖管的資源量。透過衛星遙測海面溫度與絕對動力高度推算之絕對地轉流資料的分析，可以歸納出在鎖管主要產卵時期常常會有發生黑潮入侵東海南部大陸棚區的狀態，黑潮表層相對溫暖的海水被帶進湧升流區造成表水溫異常升高；再從風場資料與地轉流場、海面高度、海表溫的變動時序分析，推論造成黑潮入侵的原因包括：冬季在東北季風持續作用下向岸(向西北)的艾克曼輸送、東海陸棚水因冷空氣南移而冷卻下沉並順應大陸坡地形流出陸棚區，表層黑潮水作為補償向湧升流區靠近以及中尺度渦旋向西位移影響黑潮等。另外2012年與2016年沿著中國大陸東南海岸南下的中國大陸沿岸流比較強，為湧升流區帶來更多冷水，結果造成鎖管資源量在這兩年比較低的主要原因。由本研究分析得到的結果，希望可以做為預測臺灣東北部黑潮是否能入侵陸棚區的依據，並進一步做為預估鎖管資源量的參考。

關鍵字

劍尖槍魷；鎖管捕捉量；湧升流區；黑潮入侵；冷水入侵

並列摘要

The purpose of this study is to discuss the physical ocean factors and the driving force that cause the annual resources variation of the swordtip squid in the upwelling area off northeastern Taiwan and the southern continental shelf of East China Sea. The hydrological data from the tide gauge station at Peng-Jia-Yu in the southern East China Sea, combined with satellite remote sensing data, meteorological observation data at Peng-Jia-Yu, and capture data of swordtip squid were used. The fundamental physical factors include the change of monsoon, the mainstream position of Kuroshio east of Taiwan, the northward current from the Taiwan Strait, the southward China Coastal Water in winter, and the westward-propagating mesoscale eddies from the North Pacific Ocean. Results from this study indicate that there is a positive correlation between the water temperature at Peng-jia-yu and the squid resources in October of the previous year and April in the year, because swordtip squid usually migrate to the upwelling zone for growing and spawning during March to May and October to December each year. The higher the water temperature, the faster the squids will grow and then increase the amount of resources. Through the analysis of sea surface temperature (SST) and geostrophic current estimated by absolute dynamic topography, we verify that when the positive surface water temperature anomaly in the upwelling area is normally associated with the Kuroshio intrusion. The dynamics of the Kuroshio intrusion is attributed to the onshore Ekman transport induced by the northeasterly winds during the winter monsoon, winter cooling-caused joint effect of baroclinicity and relief (JEBAR effect) in the shelfbreak northeast of Taiwan, and the impingement of cyclonic eddies on the Kuroshio. Our analysis also suggests that the China Coastal Water which moves southeastward along the coast of China were relatively strong and bring more cold water to the upwelling area in the winter of 2012 and 2016, and consequently the catch of squids was decreased. The results of this study are expected to be useful to the estimate of the swordtip squid resources.