蜜芽传媒

For one animal, the journey of a lifetime is about to begin. The rivers of North America are home to a creature that has one of the toughest journeys in the animal kingdome. Millions of these fish are heading for home. Coming from all over the north Pacific, and navigating with unbelievable accuracy, they're returning back to the individual rivers where they were born. They've spent around two years out in the open ocean, pumping themselves up for this one mission. This trawler is here to find out how many salmon are coming in this year so they can set the size of the catch. The numbers are mind-boggling - they calculate 12 million salmon streaming into this one river system. These sockeye have got their breeding heads on and the only thing they can think about is reaching their spawning grounds. But their target is over 700 miles inland. To get there, the salmon are going to need every ounce of energy, and unbelievable determination. You'd think that after such a journey they'd be able to relax by the time they got to a few miles from their spawning grounds, but in parts of the river 2,000 thousand tons of water boils over the rocks every second creating some of the world's biggest white water. And the salmon have to really start burning energy to fight their way through it. In fact, they need so much energy they actually start to digest their own bodies. After half an hour's kayaking here, presenter Steve Leonard is completely shattered, yet the sockeyes keep this up for weeks to reach their destination, until they're running on empty. As they make their way upriver they also change into their spectacular mating display colours in a final flourish. The female lays the eggs, the male fertilizes them and that's it - all these exhausted fish go, literally, belly up. For the sockeye salmon it's a one-way ticket. Of the millions of fish that start this journey, every single one of them will die.