ENSO对长江口日本鳗鲡苗捕捞量的影响

ENSO是一种对世界渔业有重要影响的气候事件，对长江口日本鳗鲡苗的捕捞量也有一定影响．本文通过对1974～2003年的Nineo 3．4区的表层海水温度（SST）和长江口日本鳗鲡苗的捕捞量进行相关分析，以揭示彼此的相关性．1974～1982、1983～1993年崇明的鳗苗捕捞量和ENSO指标值基本成相反关系．1992—2003年长江口鳗苗总捕捞量和ENSO指标值也基本呈相反关系．此期厄尔尼诺发生时，鳗苗总捕捞量明显降低，而拉尼娜发生时则明显增加．进一步建立Nineo3．4区的水温距平值和当年鳗苗捕捞量增量关系，发现随着水温距平值增大，1974—1993年鳗苗捕捞量增量呈现增加趋势，但相关性并不显著．将其中3个强厄尔尼诺年的数据去除，则呈显著相关．相反，1993～2003年间，随着太平洋Nineo3．4区水温距平值增大，上海鳗苗捕捞量呈减少趋势，但相关性不显著，分别去除个别年份后则呈显著下降趋势．这主要是因为前一阶段是以拉尼娜事件为主体，水温距平值一定程度的增大，鳗苗捕捞量呈现增长趋势；而后一阶段主要以强厄尔尼诺事件为主．再采用当年鳗苗捕捞量增量和去年太平洋Nineo3．4区全年水温距平值建立相关，得出长江口鳗苗增量随去年水温距平值增加呈现显著上升趋势．其原因主要是由于ENSO影响长江口水温分布，而鳗苗补充需要一个最适温度范围．这进一步验证了非厄尔尼诺年后发生厄尔尼诺次年属鳗苗增产年度的理论．这些结果表明可将Nineo3．4区海表温度作为长江口日本鳗鲡苗捕捞量预测指标．

Impact of El Nino-Southern Oscillation events on the catches of glass eel (Anguilla japonica) in the Yangtze Estuary

The ENSO is defined as a natural oscillation of the coupled ocean-atmosphere system in the tropical Pacific. To predict the catch or production of glass eels （Anguilla japonica）, we build relationships between the catches of glass eels and the SSTA in Nineo 3.4, based on the history data of glass eels and the SSTA in Nineo 3.4. There is significant negative correlation between the ENSO indices （SSTA） and the catches of glass eels in surrounding waters of Chongming Island or in all estuary of Yangtze River in Shanghai in 1974 -1982,1982 - 1993,1992 -2003. The catch of glass eels showed a pattern of low catches during E1 Nineo and high recruitment during La Nineo. Also, when the data in several strong El Nineo year is left out,the catch increment between two years has a positive relationship with the SSTA of the present year in 1975 - 1993. It shows an inversely correlated with SSTA of the present year in 1992 and 2003 while it is a positive one with a 1-year lag from 1992 to 2003. So,it results that the year next to E1 Nineo is the year of catch increment for glass eels. The potential explanatory mechanisms for such relationships between catches and climate are investigated. This may attribute to the temperature distribution near the Yangtze Estuary where the waters may be influenced indirectly by the ENSO due to the surface water of Taiwan warm current.Thus,by evidence of ENSO-related recruitment of Japanese eels in the Yangtze Estuary the eel catch in the estuary can be predicted from the SSTA in Nineo 3.4.