Welcome to assignment on the BBC World Service. I'm Heath Drusein.

I'm on an old school bus in the tiny mountain hamlet of Stanley Idaho.

The bus is there as part of the town's annual Sawtooth Salmon Festival.

My fellow passengers are buzzing with excitement as we get ready to go find some fish.

Salmon are a huge deal in America's Northwest. You've probably seen the images of them hurling

themselves out of the water upriver rapids. This is exactly where that happens, or at least where it

happens for now. We're going to talk about life cycle, we're going to talk about how the salmon

are doing. Feel free to ask your questions and this ought to be fun. As our bus rumbles onto a

two-lane highway, the jagged Sawtooth Mountains dominate the sky to our right. On our left,

the crystal clear waters of the aptly named salmon river Meander along the road. I find myself

sitting next to the salmon Yoda himself, Dave Canemella, a retired fishery's biologist who studied

salmon in the region for decades. Are we likely to see some fish today out there? We're going to

see some reds, reds as you know are nests. The females dig a red REDD. That's where she'll

deposit the eggs and then they'll hatch. Those fish spend about a year, year and a half,

and fresh water at which time they migrate to the ocean. If they don't get to the ocean in their

own time, in their own way, then they are subject to mortality. That is the primary cause of the

extinction trajectory that snake river salmon are on right now. And that's why I'm here.

The treasured Chinook and Sakai salmon of the Pacific Northwest are dying out. Both fish are on

the US endangered species list and time is running out to save two of the world's great animal migrations.

For this week's assignment, I'm going to explore the human factors that are driving

these iconic species to the brink of extinction. As we step off the bus on the banks of the salmon

river, it's a peaceful scene. River banks are dotted with pine trees giving way to sage rush-covered

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