水温变动对2009年西北太平洋柔鱼产量下降的影响

Influence of Variability of Temperature on Decline of Catch for Ommastrephes bartramii in the Northwestern Pacific Ocean in 2009

分布在西北太平洋的柔鱼是我国远洋鱿钓渔业的重要捕捞对象,近些年来其产量一直处在稳定的水平。然而,2009年8～10月旺汛期间在传统作业渔场(150°E～165°E、38°E～46°E)柔鱼产量出现大幅度下降,其日产量仅为正常年份的一半。为此,根据2007～2009年8～10月我国在西北太平洋鱿钓生产数据,以及产卵场表层水温,探讨2009年柔鱼产量下降及渔场变动的原因。研究表明,其产量出现下降的原因可能有2个:(1)柔鱼产卵场(20°N～30°N,130°E～170°E)黑潮大弯曲的发生,使得21℃等温线向南偏移,使得柔鱼资源补充量受到影响,从而使得渔汛期间柔鱼产量的下降;(2)旺汛期间(8～9月)传统作业渔场(42°N～46°N,150°E～165°E)的100m水层有一个明显冷水南下,分布位置为154°E～156°E,将传统作业渔场(150E～165°E)一分为二,向南的前锋(水温低于5℃)到达42°N,明显不同于正常年份,使得作业渔场的范围明显缩小,不适合柔鱼的集群,导致产量出现大幅下降。

The red flying squid （Ommastrephes bartramii） widely distributed in the North Pacific Ocean is a main fishing target for Chinese distant-water squid jigging fisheries. The production has maintained a steady level in the recent years. However, it declined sharply in the traditional fishing ground during the main fishing season （from August to October） in 2009, and the daily catch was only half of that in the normal years. Therefore, based on the catch from the Chinese squid jigging vessels and environment data in the northwestern Pacific ocean from August to September during 2007 to 2009, the study on the decline of catch for O. bartramii and variability of fishing ground in 2009 were made. The results indicated that there maybe two reasons causing a sharp decline in catch： （1） The occurrence of the big bending of Kuroshio at the spawning ground （20 - 30° N, 130 - 170° E ） caused a sharp decline in squid recruitment; （2）During the main fishing season （August-September）, the cold water （located at 154°- 156°E） at 100 m depth intruded southward into the traditional fishing ground （42 - 46°N, 150 - 165°E）,which split the traditional fishing ground into two parts. And its southerly front （temperature at 100 m layer 〈 5 ℃） reached at 42° N, which was distinctly different from that in normal years. Since the above reasons, the fishing ground has been significantly narrowed and not suitable for squid to aggregate.