The role of circadian rhythm on the fish school of larval stage

形成鱼群的过程被确定为与鱼苗的昼夜节律和海洋的物理流动条件有关。凤尾鱼幼虫的水平分布密度在统计学上表现为表层的集中分布。垂直剪切流条件改变了水流的形态，表现为各深度的流向不同。垂直剪切流是用8个垂直管测量的两个不同的层，表面和10m深。近地层的浮游物向西北方向漂移，而10m层的浮游物向南漂移。这一事实表明，如果鱼苗按照昼夜节律垂直迁徙，它们不会被水流驱散，因为在夜间，它们上升到表面并向北漂移，而在白天，它们可以在更深的层返回南方。开发了一种新的仪器，可以全天自动测量鱼苗的行为。

The process being formed a fish school was determined to correlate with the circadian rhythm of fish larvae and physical flow condition of the sea. The horizontal distribution density of the anchovy larvae was indicated statistically as the concentrated pattern in the surface layer. The pattern was changed by the vertical shear flow condition which was shown as the different flow direction in each depth. Vertical shear flow was measured two different layers, surface and a 10 m depth using 8 drogues. The drogues in the surface layer drifted toward northwest while in the 10 m layer they drifted toward south. This fact suggests that if the fish larvae migrate vertically in accord with the circadian rhythm they do not be dispersed by the flow since in night they rise to the surface and drift toward northern direction while in day time they can return toward southern direction in deeper layer. A new apparatus was developed to measure automatically the behavior of fish larvae throughout the day.