Hard lessons from the mighty salmon runs of Bristol Bay

The world’s longest ongoing salmon research reveals the astounding complexity of wild ecosystems.

  • Alaska Salmon Wildlife Ecosystems Bristol Bay Daniel Schindler Pebble Mine Wood River

    Jonny Armstrong
  • Thousands of salmon converge at a the mouth of a tributary stream in Lake Beverley's Golden Horn, just above Lake Nerka, for the final ascent to their spawning sites.

    Jonny Armstrong
  • A fox captured on a wildlife cam in the Bristol Bay ecosystem..

    Jonny Armstrong
  • Scientist Daniel Schindler and his daughter, Luna, watch the "red wave" of sockeye salmon navigate up Sam Creek, home to one of the earliest-spawning populations in Alaska's Bristol Bay ecosystem.

    Jonny Armstrong
  • Researchers measure salmon specimens captured in the Bristol Bay ecosystem.

    Jonny Armstrong
  • The University of Washington research camp on Lake Nerka, a remote but ideal location amid the Wood River system's interconnected lakes and creeks.

    Jonny Armstrong
  • Daniel Schindler is in his 17th year in the field along the rivers and streams of Alaska's Bristol Bay ecosystem. Along Lynx Creek, for instance, he nets and assesses small "resident fish" that don't migrate but get much of their nutrition by gobbling salmon eggs.

    Jonny Armstrong
  • University of Washington graduate students Neala Kendall, front, and Rachel Hovel cut open the heads of spawned-out sockeye salmon to remove their otoliths, tiny calcified discs that reveal their age and how long they lived in the ocean.

    Jonny Armstrong
  • At their spawning sites, female sockeye salmon arrange gravel nests called "redds" and males battle to decide who gets to mate.

    Jonny Armstrong
  • A homemade wildlife cam captures a grizzly bear scavenging a salmon on Yako Creek at Lake Aleknagik. This salmon had been injured by a commercial fishing net deployed at the river's mouth but kept swimming until it died and washed up on the mid-creek gravel bar. The migrating salmon are tough – some suffer bear bites and wriggle free to live long enough to spawn.

    Jonny Armstrong
  • Researchers, including Daniel Schindler and his daughter, Luna, right, relax at camp after a day in the rivers and creeks of the Bristol Bay ecosystem, where roughing it includes, surprisingly, fresh mangos, front left.

    Jonny Armstrong
 

Wood-Tikchik State Park, Alaska

When Daniel Schindler was 6 months old, his parents took him on an adventure: They moved into a tent at a research camp in the Canadian backwoods, surrounded by dozens of lakes. His father, limnologist David Schindler, was measuring how those lakes were harmed by phosphate detergent runoff and acid rain; the work he did would help lead to the reduction of those pollutants across North America. The family spent four months at the camp every year, abandoning tents for cabins once they were built. Young Schindler did a lot of fishing and swimming, and around age 14 he got interested in the science.

Now, 44 years after that first adventure started, Schindler has become the kind of scientist who can pilot a 90-horsepower jetboat across a huge lake and into a shallow meandering river, goosing the throttle while standing up to read the riffles ahead of him, zooming from bank to bank, finding the least-risky course through barely submerged rocks and snags as the waves buck the boat into the air and a cold rain pelts him the whole way.

I saw Schindler enjoying this experience in August, when I visited his research camp here on Lake Nerka, in southwestern Alaska, in an area managed as Wood-Tikchik State Park and Togiak National Wildlife Refuge. The camp is a cluster of cabins far off the grid, reachable only by boat or floatplane. The landscape feels prehistoric – more than 6 million acres of wilderness with hundreds of streams and lakes. Lush peaks, never entirely snow-free, rise steeply from the shores. It's the kind of natural setting that encourages you to breathe in more deeply than usual.

Schindler makes his living as a professor of aquatic and fish sciences at the University of Washington in Seattle, but he still embraces the rhythm of his childhood; this was the 17th summer he's spent researching this nearly pristine Alaska ecosystem. Reflecting on the path he's taken, he said, "I like being outdoors. I wanted an interesting life."

That commitment and eccentricity were shared by the outdoorsy grad students on Schindler's research team, as well by as his wife, Laura Payne, a bird biologist, and their pink-booted 9-year-old daughter, Luna, who's been their companion in this camp since she was an infant. Fellow UW professor Lorenz Hauser, an Austrian-born population geneticist, was on his 10th summer of research here, speaking English with an Arnold Schwarzenegger accent that even he finds amusing. And he'd brought along his girlfriend, Ronel Nel, a South African sea turtle biologist, who eagerly pitched in even though there are no sea turtles in this ecosystem.

Sockeye salmon are the keystone species here. The scientists study how salmon live, and how other creatures depend on them, including predators such as grizzly bears, which occur in densities 10 or 20 times higher than in Glacier and Yellowstone national parks, and seagulls, bald eagles, osprey, foxes and otters. They also study the insects and plants and water chemistry – all the factors that determine the ecosystem. "This isn't rocket science," Schindler likes to say. "It's a lot more complicated."

Until I met Schindler, I thought I was up to speed on salmon ecosystems from my decades of work as an environmental journalist in the Lower 48's version of wildness. There are six salmon species, and all of them are in trouble in the Lower 48. I've interviewed people involved in salmon recovery and visited hatcheries and dams. I'll never forget my first glimpse of sockeye back in the 1980s, when I watched a few big ones thrashing up an Idaho stream, completing their 900-mile migration from the ocean back to their spawning sites around Redfish Lake. I have since tracked the dwindling of that run, but like many conservation-minded folks, I still considered the Lower 48's millions of acres of habitat a good place for salmon to make a comeback.

Schindler had shaken up my thinking in February when he visited Montana State University, a few miles from my house, to show slides about his Alaska research. Watching his presentation, I began to see that the restoration efforts I'd reported on were kind of desperate, almost pathetic. The Lower 48 will never regain the kind of wildness that survives in Alaska. Joining his research team for several days, I experienced how Alaska is what the rest of the West used to be. And I was struck by the purity of the human endeavor itself, the scientific quest for knowledge that is such a contrast to the quest for money that dominates the civilized world.

Clad in waders and armed with bear spray, besieged by mosquitoes and yelling, "Hey, bear! Hey, bear!" to warn any lurking bruins that I was coming, I slogged with the scientists up cobble-bottomed creeks where thousands of big mature sockeye glowed psychedelically red. They turn that color for their final days, as if they're flaming out at the end of their exhausting migration from the ocean back to their home waters, intent on spawning where they were born years ago. Some of the streams were so shallow and narrow, they seemed to contain more fish than water.

We counted salmon, not only in the creeks but also in areas along the lake shores where some preferred to spawn. We netted and measured and tagged them as they thrashed in our hands, and recorded their eventual deaths from predators or exhaustion. A typical narration to the note-taker, by a scientist examining a single female carcass left on a streambank: "AW" ... "K2" ... "BK" ... "belly 10 percent!" (Translation: AW is the tracking number on the plastic tag they'd attached to this salmon the previous day, when it was alive; K2 indicates the creek segment where the carcass was found; BK means "bear kill," as shown by teeth marks. And check it out: The bear chomped out only the eggs, the richest nutrition, and discarded 90 percent of the fish.)

We also netted different species of fish and recorded their basic data, including stomach contents. The method for that: Grab the slippery fish, stick the tube from a squeeze-bottle of water into its mouth and flush the stomach contents into a pan; then release the fish back into the stream. "Grayling" ... "182" ... "62" (species, length and weight) ... "17 black fly adults, 10 caddis fly larvae, one stone fly nymph, 10 midge pupae, and salmon eggs" (what this particular grayling had eaten lately).

The scientists climbed trees to retrieve memory cards from cameras positioned to shoot photos and video of predators gorging on the salmon (when reviewing the images, scroll past the vegetarian moose that wandered through the frame). They clipped fins off fish so the DNA could be recorded, to track not only individual fish, but also generations of offspring over the years. They used tweezers to extract otoliths – the tiny stones in a salmon's skull cavity, formed by the minerals it swims through – which can show not only where a salmon traveled in fresh- and saltwater, but also the timing of its movements.

This kind of science is incredibly laborious, requiring high tolerance for immersion in cold water, hours in the rain punctuated by blasts of sunburn, swarms of stinging and biting insects, and the constant risk of irritating a bear, even in camp. (One evening we watched a bear swim across the bay and pad ashore into the brush on our side; a few weeks earlier, within sight of our camp, a bear killed a moose calf while the mother moose circled helplessly.) You also have to put up with fragrant outhouses and the lack of electricity, as a generator and solar panels provide only a few hours of juice per day. The fieldwork is less Herculean than Sisyphean; day after day, the scientists push the boulder up the hill, gathering precious data for later analysis and re-analysis and re-re-analysis.

All this work reveals an underlying truth: The sheer complexity of inter-related species and habitat is essential for an ecosystem's health, particularly for resilience to stresses like climate change. And the inverse is also true: When you "coarsen" an ecosystem (Schindler's term) by introducing roads that carve up the habitat, channeling streams, erasing wetlands, and bringing in mining projects, new transmission lines, more buildings, more traffic and so on – as we've already done in most of the West, and as is proposed for the headwaters of part of this area – the ecosystem weakens and may even collapse.

The University of Washington's Alaska Salmon Program is billed as "the world's longest-running effort to monitor salmon and their ecosystems." UW scientists began working here back in 1946, and generations of them have returned every year since. They have six camps in the area, concentrating on the Wood River, which they consider a proxy for the eight other major rivers that also flow into the saltwater of Bristol Bay – a megasystem collectively hosting the world's best sockeye runs.

The only system comparable in the Lower 48 is the Columbia River and its tributaries, stretching from the Oregon coast to headwaters in Idaho and Canada. Coarsened by more than a hundred big dams and vast modifications to floodplains and wetlands, the Columbia supports roughly 1 to 2 million migrating salmon in a good year – 10 percent of the number it used to support – and most of them are raised in hatcheries and injected into the system like a shot of methamphetamine. In Alaska, most salmon runs are still near the historical highs. The Wood River system alone – an area less than one-one-hundredth the size of the Columbia – averages 2 to 3 million sockeye per year, and sometimes hits 10 million. And they're all wild.

Commercial fishing boats hovering near the Wood River's mouth capture 60 percent of the migrating sockeye, on average, yet enough make it past the fishermen to form "the Red Wave" – a huge pulse of sockeye in the river and associated streams and lakes that supports the abundance of predators, from bears down to the blowflies that lay eggs in salmon carcasses so their maggots can feast. Scientists have found that a single carcass can support 50,000 maggots, which, in turn, are consumed by other insects, birds and fish.

The first scientists here "developed an integrated view – what we would call 'ecosystem science' today," Schindler told me. "The strength of our program is the long-term measurements," with the continuous studies generating "immense data sets."

The program's current luminaries include gray-haired Thomas Quinn, the author of a definitive textbook, The Behavior and Ecology of Pacific Salmon and Trout. He helped establish how salmon navigate far out in the ocean and then return to their home streams: They sense geomagnetic fields in the ocean and smell distinctive odors in freshwater, which lead them back to the exact spot where they hatched. Some of this information is genetically passed to offspring, Quinn believes.

The salmon face very long odds. The average spawning female lays 3,000 eggs. To maintain a healthy population, at least two of those offspring need to grow up and return to spawn a new generation. That doesn't always happen: Bears kill an astounding number of the Wood River sockeye that make it past the fishermen, ranging from 5 percent on the river itself to as much as 90 percent on the tiniest creeks. Once the bears' initial hunger is sated, they become connoisseurs, often chomping out only the brains of the males and the females' eggs. Scientists calculate that salmon flesh provides a respectable 2 kilojoules of energy per gram, while the eggs and the brains provide 10 kilojoules per gram. "Bears are omnivorous," Quinn said, "but nothing is as predictable and rich as salmon."

As the ripples of the Red Wave spread, the predators transport the dead salmon and their eggs around the ecosystem: Bears carry the carcasses a short distance, spreading nutrients in the riparian area, while gulls take fragments and salmon eggs longer distances to their nesting places, where they enrich little islands and lakes, providing food for snails and Alaska blackfish. Scientists have even found "salmon signatures" embedded in the feathers of songbirds, because nutrients derived from salmon feed the plants that produce berries the birds eat.

Jonny Armstrong, a post-doc working with Schindler, dispensed this expert advice about how it all fits together, pointing to a salmon carcass: "When you find a dead salmon that still has its eyes, you know you're tight on a bear." Translation: Gulls quickly discover salmon carcasses left by bears, and they peck out the fishes' eyes, so if you find a carcass punctured by big teeth marks and its eyes are still intact, you know that you just scared off the bear. It's probably hiding in the bushes waiting for you to move on. The gulls will arrive any second.

The complexity of this wild ecosystem begins with the water in the hundreds of creeks that form the rivers of Bristol Bay. Each creek draws from a different ratio of snowmelt, summer rains and fall rains. When some creeks are low due to a dry summer, others will likely be normal or high, which means the average is more consistent than you would expect looking at just one or two of them. The same goes for the nine rivers: Their average total flow is more reliable than any individual river.

The natural topography and geology are also complex. Some creeks rush down super-steep mountain valleys, while others dawdle down gentler grades from little spring-fed lakes; some drain volcanic soil and others don't; some are colder and some are warmer. This provides a varied habitat for salmon to exploit.

Hiking up Lynx Creek one day, above Lake Nerka, Schindler explained the "hydrological complexity" of just this single creek. It has a cold tributary (roughly 44 degrees Fahrenheit) fed by groundwater, a warm tributary (65 degrees) originating in a small headwaters lake, and a general mosaic of relatively warm pools and cold rapid segments, plus much warmer pools off the main channel, where young fish get stranded in low flows. This complexity provides "refugia" during varying weather and flow conditions, Schindler said. When a tributary floods with rains, for instance, the juvenile salmon attempting to feed in it leave, hanging out in the main channel just above the confluence – "a velocity refuge" – until the flood subsides. If the whole main channel floods, they seek sanctuary in the side pools that are barely connected to the main.

I sat on a bank at the confluence of Lynx Creek and its cold tributary, where bears had flattened the grass and left portions of carcasses, and watched sockeye swim up to me. In many places, the water was so shallow that it didn't even cover their humped backs and dorsal fins. In brief stretches that were merely soggy gravel, the fish wriggled, rather than swam, uphill. Some turned left at the confluence to go up the cold tributary and spawn there, while others kept going up the main channel, heading for higher segments or the headwaters lake, to spawn in warmer water. Those spawning in the cold tributary are genetically distinct from those spawning in the main channel – one data set that supports the conclusion that the locator information is passed on to offspring. "We're discovering the genetic diversity of salmon also benefits the consumers (predators)," Schindler said. If salmon can't spawn in one segment of the creek for some reason, the other segments might be OK, so the predators can find salmon pretty consistently during the run in this creek.

Even the timing of salmon runs is complex. Some creeks have early runs, in June and early July, some have middle-of-the-season runs, and some have late runs, in August. Runs on the spawning sites in the river itself last into September, and runs on the lakeshores, where some fish spawn, last into October. Each run hits its peak for two to three weeks, but because the timing is staggered, the run for the whole Wood River system lasts eight weeks or longer. The predators have learned to roam around the fenceless, roadless miles, hitting each creek, river segment and lake at its peak, Schindler said.

The salmon's varying life cycles also lend resilience to the system. Of the offspring from a single batch of sockeye eggs, some will stay in the freshwater for a year, while others linger for two years. Once they migrate out, some spend two years in the ocean, some three. So one batch of eggs can produce salmon that return to that exact spawning site three years later, four years later, and five years later, providing multiple opportunities to successfully reproduce at that site. Schindler made this point tangible on Berm Creek, which has a persistent sandbar where it meets Lake Nerka. A few years ago, a flood deposited so much sediment on the sandbar that it completely closed off the creek to spawning salmon. No problem for the ecosystem: Other creeks did well that year, and the next spring's runoff was strong enough to blow an opening in the sandbar, allowing the next run to return to every spawning site in Berm Creek. Ultimately, the one-year disaster didn't matter.

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