Chinook salmon travel 1900 miles along the length of the Yukon River twice in their lifetimes, from their spawning grounds near Whitehorse, Yukon, to the Bering Sea and back again.
The first wave of Chinook salmon arrived at the Yukon River delta on June 12th this year, with half of the run expected to have passed into the river by June 20th. Ice, water temperature and wind affect the timing of the migration. The first Chinook passed through the Whitehorse fish ladder on August 5th, 2026.
The Whitehorse hydroelectric dam is the only human obstruction along the entire course of the Yukon River. It lies 100 km downstream from prime Chinook spawning habitat. The world’s longest wooden (!) fish ladder was built at the same time, rising fifty feet over its 1/4 mile length. Fish viewing windows (see the live stream here) allowed staff to count and sex fish as they pass through the ladder. In 2023, cameras were installed that now do this job 24/7.
The eggs (roe) that these fish lay will hatch in icy waters three to five months from now. The young fry will spend the next year in the freshwater of the Yukon River growing and gaining strength for their journey to sea. Once they enter the brackish, braided river mouth, they linger again, growing and adapting to the saltwater. They are called smolts now.
Adaptable & Resilient
After entering the Pacific Ocean, they travel north to the Bering Sea, even as far as the Chukchi Sea in Russia, feeding on the ocean’s bounty. They’ve been found swimming one thousand feet below the surface! It seems an odd adaptation to start and end life in a river, far from your adult home, if you’re going to be a predator big enough to need the expanse of the ocean’s buffet to sustain you. But they’ve been doing it for four to six million years!
After five to seven years in the ocean, the salmon return to the Yukon River. Nobody knows what prompts them to leave the ocean or how they find their way from thousands of miles out at sea back to the river mouth. Once they’re in the river and get “close” to their natal streams, their sense of smell guides their final journey. Each river tributary has a unique blend of minerals and organic materials that creates a distinct scent. That is what guides the salmon. (A bone in their ear, called an otolith, also holds this same unique chemical composition. If a researcher has the otolith, they can tell where that fish was born!).
Chinook salmon begin sorting themselves two hundred miles before the first major branch in the Yukon River. The fish that will go up the tributary start swimming on the left side of the river, while the ones that will continue on start swimming on the right. A small percentage of salmon stray. Usually, it’s the males. (Seriously!) Some find their way back to their route, and others spawn someplace new. This probably helps to maintain genetic diversity within the species.
Salmon Feed Forests
The salmon swim an average of thirty miles/day into the current and over rapids to their spawning grounds in a journey that takes two to three months in the river. It’s tiring just to think about it. The whole while, their bodies are deteriorating. They lose their steel color, turning bright red to deep purple. They don’t eat. Their muscles start breaking down when they leave the saltwater. The process speeds up once they reach their natal streams, and they die shortly after spawning. They pay the ultimate price to complete their journey.
In completing their life cycle, not only do they give life to the next generation, these salmon also deliver the nutrients of the sea to inland forests. In areas where soil health is poor, tree growth can depend almost entirely on nitrogen supplied by migrating salmon. Overall, 70% of nitrogen along inland streams comes from the ocean, transported in this incredible journey. 
That’s the answer to why an adult predator who needs the expanse of the ocean’s buffet is born and dies in a river far from their adult home. It’s all connected. We’re all connected.
If you’re interested in purchasing or licensing any images you see here, please email me at SNewenham at exploringnaturephotos.com, and I’ll make it happen.
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I feel like that sign showing 28 total salmon is the huge elephant in the room, Sheila. Can you elaborate on that? Am I missing something?
The salmon enter the river in June and start arriving at the Whitehorse fish ladder in August. This year, the first salmon arrived in Whitehorse in August 5th. I took that picture on August 7th. As of August 24th, more than 560 chinook had passed through. It is one of the strongest runs in recent years, following lower numbers almost every year since 2020.