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

52. Free from competition,
    由于没有竞争
53. these giants can dine alone.
    这些大家伙得以独自享用美食
54. Pickings are usually thin for the salamanders,
    大鲵的收获通常都比较少
55. 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
56. The salmon have arrived.
    鲑鱼来了
57. 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
58. 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

来自《行星地球 第一季 第三集 Planet Earth S01E03 淡水》第 55 行