台灣地區鯖鲹圍網漁獲之年際變化及相關氣候變化特性

Interannual Variability of Mackerel Purse Seine Fishery of Taiwan and its Associated Climate Changes

蔡清彥(Ching-Yen Tsay) ； 陳昭銘(Jau-Ming Chen) ； 陳金華(Chin-Hwa Sun)

《大氣科學》 29卷4期 (2001/12) Pp. 379-394

摘要

本文研究台灣地區鯖鰺圍網漁獲之年際變化及相關大氣-海洋系統之氣候變化特性，鯖鰺圍網漁獲於每年9月到次年1月達到盛產期，此時主要漁區位於台灣東北海域(121°E-125°E,25°N-27°N)。本文以9月-1月之平均每網次漁獲量(CPUE, catch per unit effort)為分析對象，該漁獲量於1982-98年之年際變化與台灣-日本間長方形海域(122°E-130°E,22°N-34°N)之海溫變化具有高度關聯性，將此海域依台灣-日本二地聯線（122°E，25°N聯到130°E，32°N）劃分為西北、東南二區，當西北海域偏暖、東南海域偏冷或西北海域較東南海域偏暖時，有利於漁獲增加，反之當海溫南北對比為相反狀態時，則漁獲傾向減少。若取此二海域海溫區域平均値之溫差（西北-東南），該海溫溫差値與CPUE二者時間序列之相關係數高達0.5，顯現此溫差値可供做為診斷漁獲變化之參考指標。
於與漁獲變化相關之台灣-日本間海域，其海洋-大氣系統變化主要係由海洋主導，以多產年為例，當北方海域偏暖、南方海域偏冷時，北方暖洋面促進水汽向上蒸發，增加潛熱通量向上傳送進入大氣，大氣系統對應形成低壓、輻合距平中心，而南方偏冷洋域則形成高壓、輻散距平中心。在此南北分佈狀態下，風場與輻散風距平均由南向北吹，不僅降低北區冬季東北季風強度，亦將熱帶水汽往北傳送，讓北方海域之大氣總含水量增加，藉由輻合距平之舉升機制，降水量亦隨之增加，而水汽遞出之南方海域則是二者皆減少。
台灣-日本間海域冬季海溫距平北暖南冷為漁獲多產年之主要變化特徵，由於海溫變化具有緩慢持續性，此變化特徵於該年春季與夏季即可發覺，因此可適當應用海溫南北變化特徵做為預報漁獲變化之可能因子。

關鍵字

鯖鲹圍網漁獲 ； 年際變化 ； 氣候變化

並列摘要

The purpose of this study is to examine the interannual variability of the Mackerel Purse Seine fisheryof Taiwan and its associated climate changes of the ocean-atmosphere system.Since the major fishery periodis between September and January,the averages of CPUE(catch per unit effort)during that period for 1982-98 are used in our analysis.Results show that key condition associated with fishery variability is SST(seasurface temperature)changes over the open oceans between Taiwan and Japan(121°E-125°E,25°N-27°N).Inthis region,when its northwestern portion becomes warmer(colder)than its southeastern portion,CPUEtends to increase(decrease).Thus,SST difference between the northwestern and southeastern portions of theaforementioned open oceans between Taiwan and Japan can be employed as an index to survey the fisheryvariability.Over the SST index region,air-sea interactions are mainly driven by ocean.During the above-normalproduction years,warm SST anomalies over the northwestern portion enhance evaporation and upwardlatent heat flux and force the overlying atmosphere to form anomalous low and convergence centers,Overthe southeastern portion,cold SST anomalies are accompanied by anomalous high and divergence centers.Following the above conditions,anomalous southerlies transport water vapor to the north and cause moreprecipitation over there.The key condition for the above-normal production year is that SST anomalies over the northwesternportion are warmer than that over the southeastern portion during the winter season.However,such acondition can be detected early in the spring and summer seasons.Thus,this SST condition provides usefulinformation for the forecast of fishery variability for winter.

並列關鍵字

Mackerel purse seine fishery ； Interannual variability ； Climate changes