Sockeye and Chinook salmon make one of the world's great animal migrations, swimming 900 miles from the Pacific Ocean up 6,500 feet into Idaho’s Sawtooth Mountains, where they spawn and die - but that journey may not happen much longer.

In addition to the gauntlet of predators the fish face, from orcas to eagles, they are also running into a man-made obstacle: huge concrete dams.

Most scientists agree the dams need to go for the fish to live, but the dams provide jobs, clean energy, and an inexpensive way for farmers to get their crops to international markets.

However, US Congressman Mike Simpson, a Republican representing Idaho, has a plan to save the salmon. He wants to blow up four dams on the Snake River and reinvent the region's energy infrastructure - a plan which has been overwhelmingly rejected by his own party.

Heath Druzin investigates how a bitter fight is now playing out in America's Pacific Northwest, pitting Native American tribes and conservationists against grain growers and power producers.

Presented by Heath Druzin

(Image: Sockeye salmon. Credit: Mike Korostelev)