battle their way for hundreds of miles upstream. 奋力逆流而上数百英里

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
59. battle their way for hundreds of miles upstream.
    奋力逆流而上数百英里
60. Up here, there are fewer predators to eat their eggs and fry.
    只因上游很少有捕食鱼卵 和鱼苗的掠食者
61. A grizzly bear.
    一只灰熊
62. From famine to feast -
    它已经很久没有打牙祭了

来自《行星地球 第一季 第三集 Planet Earth S01E03 淡水》第 59 行