Department of Life Science and Institute of Fisheries Science, National Taiwan University, Taipei, Taiwan.
PLoS One. 2012;7(2):e30805. doi: 10.1371/journal.pone.0030805. Epub 2012 Feb 23.
Long-term (1967-2008) glass eel catches were used to investigate climatic effects on the annual recruitment of Japanese eel to Taiwan. Specifically, three prevailing hypotheses that potentially explain the annual recruitment were evaluated. Hypothesis 1: high precipitation shifts the salinity front northward, resulting in favorable spawning locations. Hypothesis 2: a southward shift of the position of the North Equatorial Current (NEC) bifurcation provides a favorable larval transport route. Hypothesis 3: ocean conditions (eddy activities and productivity) along the larval migration route influence larval survival. Results of time series regression and wavelet analyses suggest that Hypothesis 1 is not supported, as the glass eel catches exhibited a negative relationship with precipitation. Hypothesis 2 is plausible. However, the catches are correlated with the NEC bifurcation with a one-year lag. Considering the time needed for larval transport (only four to six months), the one-year lag correlation does not support the direct transport hypothesis. Hypothesis 3 is supported indirectly by the results. Significant correlations were found between catches and climate indices that affect ocean productivity and eddy activities, such as the Quasi Biennial Oscillation (QBO), North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation (PDO), and Western Pacific Oscillation (WPO). Wavelet analysis reveals three periodicities of eel catches: 2.7, 5.4, and 10.3 years. The interannual coherence with QBO and the Niño 3.4 region suggests that the shorter-term climate variability is modulated zonally by equatorial dynamics. The low-frequency coherence with WPO, PDO, and NPGO demonstrates the decadal modulation of meridional teleconnection via ocean-atmosphere interactions. Furthermore, WPO and QBO are linked to solar activities. These results imply that the Japanese eel recruitment may be influenced by multi-timescale climate variability. Our findings call for investigation of extra-tropical ocean dynamics that affect survival of eels during transport, in addition to the existing efforts to study the equatorial system.
利用长期（1967-2008 年）玻璃鳗渔获数据，研究了气候对台湾日本鳗鲡年度补充群体的影响。具体评估了三个潜在的解释年度补充群体的假说。假说 1：高降水会使盐锋向北推移，从而形成有利的产卵地。假说 2：北赤道流（NEC）分支位置的南移为幼鱼提供了有利的输运路径。假说 3：幼鱼洄游路径上的海洋条件（涡活动和生产力）影响幼鱼的存活。时间序列回归和小波分析的结果表明，假说 1 不成立，因为玻璃鳗渔获量与降水呈负相关。假说 2 是合理的。然而，渔获量与 NEC 分支相关，存在一年的滞后。考虑到幼鱼运输所需的时间（仅四到六个月），一年的滞后相关性并不支持直接输运假说。假说 3 间接地得到了结果的支持。渔获量与影响海洋生产力和涡活动的气候指数之间存在显著相关性，例如准两年振荡（QBO）、北太平洋旋度振荡（NPGO）、太平洋年代际振荡（PDO）和西太平洋振荡（WPO）。小波分析揭示了鳗鲡渔获量的三个周期性：2.7、5.4 和 10.3 年。与 QBO 和尼诺 3.4 区的年际相干性表明，较短时间尺度的气候变率受赤道动力的纬向调制。与 WPO、PDO 和 NPGO 的低频相干性表明，通过海气相互作用，经向遥相关存在年代际调制。此外，WPO 和 QBO 与太阳活动有关。这些结果表明，日本鳗鲡的补充群体可能受到多时间尺度气候变率的影响。我们的研究结果表明，除了现有的研究赤道系统的努力之外，还需要研究影响运输过程中鳗鱼存活的亚热带海洋动力。
