中太平洋聖嬰事件與東太平洋聖嬰事件對於太平洋熱帶鮪魚捕獲率分佈的影響

Abstract

在氣候變遷的影響下，大尺度的洋流改變會影響海表溫度分佈，而洄游性的海洋魚類可能因應溫度改變而遷徙，造成漁業資源的分佈變化。為找出海洋表面溫度之變化是否在時間及空間上影響鮪魚捕獲率，本研究選擇黃鰭鮪魚(Yellowfin tuna)以及長鰭鮪魚(Albacore tuna)做為研究魚種，使用資料為美洲熱帶鮪魚委員會(Inter-American Tropical Tuna Commission, IATTC)及中西部太平洋漁業委員會(Western and Central Pacific Fisheries Commission, WCPFC)之延繩釣鮪魚捕獲資料。研究時間及空間為1971 ~ 2016 年，緯度20°N~20°S，經度105°E~75°W，分析中太平洋聖嬰事件與東太平洋聖嬰事件下，兩種鮪魚單位努力漁獲量(catch per unit effort, CPUE)的空間和時間變化。 根據氣候模式 CGCMs的模擬，在全球暖化下中太平洋聖嬰事件的頻率會增加，使得海表面溫度上升的區域有別於過往的典型聖嬰現象，而溫度上升對於鮪魚的初期生長有很大的影響，其中溫度上升有利於黃鰭鮪魚的在西中太平洋中主要的產卵場，因此聖嬰事件有利於黃鰭鮪魚魚群量的增加。反之，太平洋中部暖水區的延伸可能會減少長鰭鮪魚的產卵場，且海平面溫度的升高將降低其增添量，因此聖嬰事件不利於長鰭鮪魚魚群量的增加。 研究結果顯示在中太平洋聖嬰事件下，長鰭鮪魚及黃鰭鮪魚CPUE之重心相較於正常年有西南向的移動; 而在東太平洋聖嬰事件下，長鰭鮪魚CPUE之重心相較於正常年有西南向的移動，黃鰭鮪魚有東南向的移動。 探討中太平洋聖嬰事件對於鮪魚捕獲率分佈是否有影響，在未來中太平洋聖嬰事件的發生頻率隨著氣候變遷而有增加的情況下，對於漁業管理以及海洋資源的永續發展將有很大的幫助。

This study selected Yellowfin tuna and Albacore tuna as the research species to explore whether the change in sea surface temperature affects the spatiotemporal variations in the tuna catch rates. We used long-line tuna fishing data from the Inter-American Tropical Tuna Commission (IATTC) and Western and Central Pacific Fisheries Commission (WCPFC). With global warming, climate models CGCMs project an increasing trend of central Pacific El Niño events, where the changes in sea surface temperature are different from the typical eastern Pacific El Niño. Such environmental changes influence the early life stage of tunas. The increase in temperature is beneficial to the main spawning ground of yellowfin tuna in the Western Central Pacific Ocean, the El Nino event may cause the increase in the population of yellowfin tuna. Conversely, the extension of the warm water in the Central Pacific Ocean may reduce the spawning grounds of albacore tuna, the El Nino event may cause the decrease in the population of albacore tuna. Results show that under the Central Pacific El Niño events, the gravity center of catch per unit effort for Albacore tuna and Yellowfin tuna have a southwestward movement compared to normal years. Under the East Pacific El Niño events, the gravity center of catch per unit effort for Albacore tuna has a southwestward movement compared to the normal year, while the Yellowfin tuna has a southeastward movement. Consequently, it is crucial to investigate how such climatic periodicity will impact the distribution of catch rate and abundance of tunas, which will greatly help fisheries management and sustainable development of marine resources.