The Longest Migration — Yukon River King Salmon

SALMON ODYSSEY

Every year, countless millions of salmon carry out one of the greatest animal migrations on earth. The longest and most remarkable of these journeys runs virtually the entire length of the Yukon River — an immense watershed that sprawls across interior Alaska and into northwestern Canada.

Some years ago, a female king (or chinook) salmon was radio tagged in the lower reaches of the Yukon River by Dr. John Eiler, a research biologist with the National Marine Fisheries Service in Juneau, Alaska. Two months later, that fish spawned in the Nisutlin River (pronounced Na-zet-lin), near the village of Teslin in the Yukon Territory of Canada.

The Nisutlin River flows through vast wild country in Canada’s Yukon Territory

Covering more than 30 miles per day against the unrelenting current, this six year-old, thirty pound salmon swam more than two thousand miles from the Bering Sea to reach her spawning grounds. Without eating, fueled only by stored fat and phenomenal inborn determination, she swam farther than the distance between San Francisco and Chicago.

I recently joined Alaskan author Debbie Miller for a canoe trip down the Nisutlin River. Debbie was collaborating with John Eiler and artist Jon Van Zyle on a beautiful children’s book called A King Salmon Journey. She wanted to see firsthand the wild landscape and the river where Eiler’s tagged chinook had ended her odyssey.

BEGINNINGS

We often think of a salmon’s migration only as the journey upriver to spawn. But in fact, the story begins much earlier…

It’s winter in the far north. The immense night sky swarms with stars, and curtains of aurora furl above the timbered ridges. The boreal forest is deep in powder snow. At this season, the Nisutlin River is a twisting, blank-white corridor closely crowded by trees.

Under the snow and beneath several feet of ice, a steady, frigid current flows, like a memory of the long-vanished summer. The blackness and silence underwater would seem as lifeless as interstellar space.

And yet, nestled down in the stream-bed, there are thousands of tiny beating hearts.

Several months earlier, pea sized king salmon eggs buried in the gravels started to hatch. The creatures that emerged looked like blunt headed mini-fish, each with a tangerine colored yolk sac bulging from its belly. Biologists call these newborns alevins, and the yolk sac is their only source of food.

The alevins require a clean and porous riverbed, so that oxygenated water can sift through the pebbles. If silty runoff from human activities clogs the gravel, alevins can suffocate and die; but they thrive in pristine northern waters like the Nisutlin River.

EDDIES AND BACKWATERS

After using up their yolk sac, the little salmon start their lives as free-swimming fish, called fry. Often hundreds of them emerge from the gravel at once and pop to the surface for gulps of air, inflating their swim bladders for neutral buoyancy in the water.

Chinook fry prefer the slow current of eddies and backwaters, where they feed on tiny zooplankton before graduating to bigger aquatic insects and larvae. The growing salmon look like bronzy minnows with dark vertical bars along their sides, called parr marks.

King salmon fry in an observation tank at the Whitehorse Rapids fish ladder

This color pattern gives them camouflage from hungry birds like mergansers, kingfishers, and loons, as well as northern pike, burbot, and other predatory fish. Chinook fry like to stay in quiet water and near the banks, where if you keep still and peer into a clear eddy they seem to materialize out of nowhere…flitting, hovering, drifting.

Watching these miniature fish, it’s hard to imagine that Yukon River kings can grow into the hulking beauties that haunt fishermen’s daydreams.

THE FIRST MIGRATION

Chinook fry spend a full year in the Yukon River before migrating to the sea. They feed avidly during their first summer, building up enough fat to carry them through the long boreal winter. Little is known about their life during those frigid months, when the still nights are interrupted by the resonant booms of cracking ice. (CLICK to hear)

In spring, the river becomes a mass of fractured, grinding icefloes that eventually give way to the open, current-slick waters of summer. The little chinooks now begin their first great journey — swimming and drifting downstream, urged along by the current. In tributaries like the Nisutlin River, crystal water shimmers across the shallows, and the deep pools take on a mysterious emerald glow.

Few things speak more clearly of wildness than wolf tracks on a Nisutlin River sandbar

The journeying fish swim past sandbars inscribed with the tracks of moose and bear, wolverine and wolf. Every footprint — and every swirl from a passing salmon’s tail — is the signature of a great unspoiled wilderness.

Young chinooks from the Nisutlin River make their way into the Teslin River, which joins the brawny Yukon near the First Nations community of Carmacks. Fry born in some upriver headwaters must negotiate a hydroelectric dam in the city of Whitehorse — the only human obstruction on the entire Yukon River system. It’s equipped with the world’s longest fish ladder — measuring 1,200 feet with a 50 foot rise. There’s also an observation window where tourists can glimpse the young chinooks on their way downstream, briefly mingling with hefty adults headed upriver to spawn.

Migrating salmon use the world’s longest fish ladder to pass Whitehorse Rapids Dam, the only human obstruction in the Yukon River system.

The nearby Whitehorse Rapids Hatchery releases 150,000 to 400,000 king salmon fry every year. All other salmon in the Yukon River system are spawned entirely in the wild.
At every confluence, young kings born in countless tributaries join the migration, together with millions of little chum and silver salmon going the same way.

The Yukon River flows across Alaska into the Yukon Territory and British Columbia.

INTO ALASKA

The Yukon is the third longest river in North America, with a vast drainage larger than the combined size of Texas and Oklahoma. Much of the Yukon is laden with suspended glacial sediment, making it the color of creamed coffee. If you lean close on a calm day, you can hear the river’s voice — a faint metallic hiss created by billions of silty shards roiling against each other.

CLICK for a short video of the Yukon River with this sound.

But it sounds entirely different on windy days, when whitecaps rush across the channels, gusts whip through the surrounding forest, leaning trees creak and rasp together, and boreal chickadees add their voices to the windscape. (CLICK to hear)

Along the lower reaches of the Yukon, dense forest gives way to grassy tundra and the river splits into multiple channels meandering across a huge, flat estuary delta. Young chinooks linger here, feeding and growing while they go through a physiological adaptation to saltwater.

The little chinooks have now become smolts, their fading parr marks replaced by gleaming silver sides and dark backs, so they look like miniature adults. This color pattern, called countershading, helps to conceal them from overhead predators looking down into the dark water, and from underwater hunters looking up toward the bright sky.

Finally, glittering schools of Yukon kings move out into the ocean, ending the first of their two great river journeys.

LIFE IN THE OCEAN

We’ve seen that salmon are born as freshwater fish, so why do they abandon the rivers and make epic journeys to live in the sea? In a word: food. For an abundant top-level predator like salmon, freshwater provides a tiny fraction of the prey that’s available in the limitless expanses of the ocean.

As they grow, juvenile Yukon River chinooks move into the northern Bering Sea, ranging from about 60 degrees latitude up through the Bering Strait; and some even reach the high arctic waters of the Chukchi Sea.

We can only imagine the distance each chinook covers during its oceanic life, probably thousands of miles. Whirling in shimmery schools, diving deeper than a thousand feet, they prey on squid, small fish, and krill.

King salmon are not only predators but also prey — for animals like seals, sea lions, belugas, killer whales, salmon sharks…and of course ourselves. If all goes well, kings can live 5 or 6 years, occasionally up to 8 years. They are the biggest salmon species, often reaching 40 to 50 pounds or more. The world record is a 126 pound chinook scooped into a fish wheel near Petersburg, Alaska in 1949.

THE SECOND MIGRATION

Think of a Yukon River chinook far off in the deep blue reaches of the Bering Sea — a prime, powerful, heavy bodied torpedo of a fish, one of the most exquisitely perfected creatures in all the oceans. Somehow, an irresistible migratory urge arises from the nerves and cells inside its body. This impulse may date back to the evolutionary emergence of modern salmon, four to six million years ago, or to even earlier ancestors.

A king salmon heading back to its home river may cover a tremendous distance — perhaps a thousand miles or more — through the vast and trackless sea. How does it find the way?

Some experts speculate that salmon might use the position of the sun, or its polarized light, as a compass. Perhaps they can orient by the direction of currents or other cues in the water itself. Biologists also know that a salmon has flecks of magnetite in its snout, so possibly it uses the earth’s magnetic field as a compass. Nobody knows for sure.

Once the fish approach their spawning river, there’s far more certainty about how they navigate. Salmon have a marvelous ability to smell the unique blend of minerals and organics in their home waterway.

How acute is their sense of smell? The Yukon and Tanana Rivers meet near the center of Alaska. From here, some kings go northward in the main stem of the Yukon, while others turn south into the Tanana. Incredibly, fish from each group already favor the north or south side of the Yukon when they pass the village of Galena — about 200 miles downstream from the confluence!

As they continue upriver, salmon detect the unique scent of each tributary, until finally they encounter the alluring bouquet of home. But this isn’t to say that every chinook navigates flawlessly back to its birthplace. In all salmon species, a small percentage of fish stray and spawn someplace new. Perhaps this helps to maintain the genetic diversity that has made salmon so successful and adaptable.

Aerial view of the Yukon River in interior Alaska.

NISUTLIN

The king salmon radio tagged by Dr. John Eiler in the lower Yukon reached the Canadian border a month later, in mid-July. She was now transforming from the bright silver of her ocean life to the vibrant scarlet of spawning season.

When she started up the Yukon, there were many thousands of king salmon in the river. But as more of them veered off into their home tributaries, fewer continued toward the headwaters spawning grounds. Eventually they passed the silty feeder streams and entered clear water again. Recent studies show that salmon use infrared light for vision in murky water, but it’s interesting to wonder what it’s like to see again the kaleidoscopic stony riverbed, the trees leaning out from cutbanks, the golden eagles soaring in clear blue skies.

A golden eagle soaring above the Nisutlin River.

Drawn by her amazing sensitivity to water-borne smells, the tagged chinook swam into the meandering Teslin River and navigated the silent depths of Teslin Lake. Perhaps she traveled in company with other chinooks, but in these days of dwindling numbers it’s easy to think she might have been alone.

On July 29, she entered the Nisutlin River delta after coming almost 1700 miles upstream, living only on stored fat…and she was still swimming 33 miles per day. She was now in the territory of Inland Tlingit people, who know the king salmon as T’á, and who revere this fish not only as a traditional food but also as a major figure in their cultural and spiritual world.

SPAWNING GROUNDS

The Nisutlin River runs through an immense, stunningly beautiful expanse of wild country. For canoe paddlers and for migrating salmon, the river alternates between slow, easy stretches and rushing whitewater riffles. Woven through the surrounding peace and silence is the voice of the river itself, the aspen leaves gently rattling, the midnight proclamations of great horned owls.

On August 17, the tagged chinook slowed and circled onto her chosen spawning grounds. Turning on her side in the clear current, she began fanning the gravely cobbles, scooping out the nest, or redd, that all salmon prepare for their eggs. She was attended by a heavy bodied male in prime crimson breeding colors, his snout elongated and hooked, his mouth arrayed with sharp teeth to fight off competing males.

The sun traced a low arc across the autumn sky and a swollen harvest moon illuminated the chill nights. For several days, the male and female carried out an ancient, exquisitely choreographed underwater mating dance — swimming side-by-side, crossing over and back, the female fanning her nest, the male defending his territory and occasionally quivering his body beside her.

When the moment was right, both fish held in the current, flank-to-flank, with their jaws wide open. The female expelled her eggs into the redd, and the male instantly surrounded them with a cloud of white, spermy milt. A king almon may spawn several times at different redds, until all of her eggs — which can number between 3,000 and 14,000 — are secure in the riverbed.
By the time they’ve finished, the male and female chinooks look thoroughly depleted, splotched with cheesy decay, swimming stiffly with ragged fins. Amazingly, the female keeps guarding her nest for some days or weeks, until her strength is gone. All chinook salmon die after spawning. Their bodies help to fertilize the rivers where their young will hatch and grow, and where they will start the longest migration once again.

MOONRISE

When Debbie Miller and I paddled down the Nisutlin River in late August, the king salmon had nearly finished spawning. We came across an exhausted female guarding her redd, struggling to hold herself against the current, until she finally drifted away downstream.

Afterward the river seemed lifeless and empty, not just because the run was over but especially because the Yukon River chinook population was near its lowest ebb. And yet, just knowing that chinooks had completed their great migration made the river sparkle with hope and possibility.

Farther downstream, we came across the carcasses of other spawned-out kings, inert in the deep pools or laid out on sandbars, scavenged by eagles and ravens, grizzly bears and wolves.

On a Nisutlin River sandbar, this partly-scavenged carcass of a spawned-out king salmon marks the end of an epic migration.

Then, as we rounded a bend in the late afternoon, an almost preternaturally wild sound came up from the nearby forest. We stopped paddling, let the canoe drift, and focused entirely on listening. It was a chorus of howling wolves.

We nudged the canoe onto a sandbar, I grabbed my recording gear, and we scrambled behind a patch of willows. Everything fell silent except for the gently murmuring river. Eventually we figured there was nothing to lose…so we cupped our hands, leaned back, and howled. The ensuing stillness felt like a rejection from the savvy wolves.

But then, to our astonishment, the voice of a lone wolf poured out from underbrush directly across the river. Most likely the dominant male had come to investigate and to announce his pack’s territorial claim. (CLICK to hear)

The wolf’s protracted howls rang out across the valley, giving voice to an enduring land where everything remains exactly in its place, uncompromised and undiminished. Where people still follow their ancient ways of harvesting the rivers and land.

And where — if we are careful and responsible and wise — Yukon River king salmon will continue their unparalleled migration to the clear Nisutlin headwaters, into a time far beyond our own.

Today, as in ancient times, king salmon end their journeys, wolves howl, and travelers watch the full moon rise above the Nisutlin River

Notes:

FISHING FOR KINGS: NETS AND TRADITIONS

It’s easy to understand why chinook salmon are also called kings. They’re the biggest salmon, esteemed for their taste, and very rich in oil (especially in the Yukon, where high fat content fuels the long migration). Not surprisingly, chinooks bring a premium price for commercial fishermen. But they’re also Alaska’s least abundant salmon, so their overall economic value lags well behind the other species.

Commercial and subsistence fishermen harvest Yukon River kings with set nets, fish wheels, drift gillnets, beach seines, and dipnets. Of course, native people had developed ingenious methods for catching chinook salmon long before the first Europeans arrived.

For example, Koyukon Indians watched for the subtle V-shaped wake made by a king salmon swimming just below the surface. Then a paddler in a small canoe would ease close to the fish and deftly scoop it into a dipnet. If this was the first king salmon of the year, people sprinkled the fish with water from a willow branch, speaking to it: “Pull up your canoe here.” This was like a prayer to the spirit of the salmon, asking more fish to offer themselves. Afterward, everyone in camp gathered for a feast of welcoming and gratitude.

Throughout the Yukon River watershed, native people from many cultural communities greet the arrival of chinooks as a major event in the passage of a year. Koyukon people honor these fish by naming the month of June Ggaath Noghe’ — King Salmon Month.

Since a time beyond memory, chinooks have been vital to indigenous ways of life and subsistence economies. Today they’re usually cut into filets or strips, then cured in smokehouses above the riverbanks. For many villagers, oil-rich smoked king salmon is one of the most treasured of all foods — a great gift from the Yukon River.

THE NUMBERS GAME

Because chinooks are so important to both subsistence and commercial fishermen, it’s big news when these fish decline. Runs were strong during the 1980s and 1990s, when the total catch of Yukon River kings ranged as high as 200,000 fish. But then came an alarming decrease. By 2008, the harvest dropped below 50,000 fish, while many chinook runs elsewhere in Alaska remained strong. In the Yukon River, catches were strictly limited so that enough chinooks would survive to spawn in the tributaries.

Nobody knows why Yukon River kings have declined, but there’s an abundance of theories. One focus of attention is the incidental take of chinooks by deepwater trawlers, but stricter by-catch limits haven’t solved the problem and many biologists suspect there are multiple causes.

The main possibilities include overfishing, low freshwater survival, poor marine conditions, and climate change. A prominent suspect is the famous El Nino (or Pacific Decadal Oscillation), which causes ocean-wide shifts in temperature and storm patterns. These, in turn, decrease the productivity of marine waters and diminish the food supply for salmon.

There’s a fascinating see-saw pattern between north and south. When ocean temperatures are especially warm off the coast of Alaska and northern British Columbia, salmon tend to thrive in these waters, while the populations decline farther south. But when conditions reverse and it’s colder up north, salmon numbers increase in the south and decline in the north. It’s also worth remembering that other factors like predation, commercial and subsistence harvests, and poor reproduction can have a greater impact when the salmon population is already low.

Good news came in the summer of 2015, when about 115,000 migrating kings were counted in the lower Yukon, and more than 83,000 crossed into Canada on their way to the upriver spawning grounds. This is well below the averages in earlier times but a big improvement over recent years. It means more chinooks for the people who depend on them, more nutrients to benefit the environment and wildlife, and more spawning fish to strengthen future runs.

By Richard Nelson for SalmonWorld