This is the world's largest fresh water fish migration. 这是世界上规模最大的淡水鱼洄游
Across the northern hemisphere salmon, returning from the ocean to their spawning grounds, 鲑鱼穿越整个北半球 从海洋回到它们的产卵地
Pickings are usually thin for the salamanders, 大鲵的收获通常都比较少
but every year some of the world's high rivers are crowded by millions of visitors. 而世界上的高山河流每年都将 迎接成千上万的来访者
detect the slightest changes in water pressure. 能觉察出最轻微的水压变化
But with the spring melt here in Japan 可是在日本 每当春雪消融之际
They're the only large predator in these icy waters. 它们是这些冰水中唯一的大型掠食动物
There are advantages to life in the fast stream - 这些动物拥有在急流中生存的先天优势
has bushy gills to extract oxygen from the current. 并依靠浓密的鳃从水中过滤氧气