Northwest

The great salmon mystery: Scientists go to unprecedented lengths to find out where chinook go

Saving salmon: Why these remarkable fish matter to the Northwest

This February 2018 file video details how for hundreds of thousands of years, wild ocean salmon have been coming to the Pacific Northwest. Now, their existence is under threat, along with the communities they support.
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This February 2018 file video details how for hundreds of thousands of years, wild ocean salmon have been coming to the Pacific Northwest. Now, their existence is under threat, along with the communities they support.

Flashing silver, the salmon loomed up from the deep, hooked and thrashing.

With a tug, scientists hauled it aboard and quickly dunked the fish in a cooler full of anesthetizing knockout potion: They had plans for this big chinook. This fish was going places, and they wanted to know where.

For as long as there have been fishermen and fish, people have wanted to know where salmon go in the sea and why, but their travels have always been a mystery. As the southern resident orcas that frequent Puget Sound battle extinction, both the whales and their primary prey, chinook salmon, are the focus of concern.

With a $1.2 million research grant from the U.S. Navy, scientists are deploying new tools to help scientists track chinook in part to better understand the travels of the whales, which are shifting.

Usually reliable summer residents of the inshore waters of the San Juan Islands, this year the whales have been seen only for a couple of brief trips since May, an unprecedented orca dearth possibly linked to a lack of adequate prey. The orcas are believed to be traveling the outer coast – in search of chinook.

Scientists are looking, too: This spring they dropped 115 receivers into the sea, weighed down with 26,000 pounds of sand in burlap bags, 3 to 10 nautical miles off the Washington Coast to track tagged fish. It’s a risky and ambitious project that starts with tossing a lot of expensive equipment in the drink.

“Seven pallets full, bloody fingers, it was just madness,” said David Huff, Estuary and Ocean Ecology Program Manager at the Northwest Fisheries Science Center of the National Oceanic and Atmospheric Administration.

“I went out and dumped $400,000 in the ocean. And I have to just trust it will still be there,” he said of deploying the receivers and other equipment. “What if it’s not? What if there’s no data? There is so much uncertainty.”

But that’s science on the open sea. “It’s a hostile environment,” Huff said. “A dangerous place to work.”

The scientists placed the receivers about 2.8 miles apart in a grid from Neah Bay to Westport. Each is about the size of a 1-liter bottle. By summer’s end, the scientists on the so-called Salmon Ocean Behavior and Distribution study also hope to tag 300 fish with a pinger – an acoustic tag that makes a crisp knocking noise – detected by the array of receivers.

The equipment on the sea floor will be listening for the tagged fish as they swim by.

Ten other fish will be tracked by satellite, everywhere they go. Scientists also will fly an underwater, unmanned glider periodically over the array to track tagged fish and record environmental information. The hope is to form diverse sources that piece together a picture not only of the movements of salmon but the possible mechanisms behind them, from the availability of food to ocean conditions including temperature.

But first, they’ve got to get tags inside the fish.

On a recent early morning at sea, biologist Joe Smith of the science center and Bill Matsubu, a scientist with National Research Council working with Huff on the project, checked on the chinook just caught aboard the Zephyr, a few miles from the toothy gray pinnacles off the coast of Shi Shi Beach. The gleaming fish was calm but not knocked out – just right for surgery. Lifting the fish to a work station set up on the back deck, they gently flushed an anesthetic over its gills while making a slit long as a pinkie nail in its belly.

The fish never flinched as they poked in the battery-powered tag, a smooth, cylinder about an inch long and big around as a pencil eraser.

Orca can hear the tag pinging. How or if they would respond to it is not known. An orca could eat a tagged fish with the tag passing through their system without harm, Huff said.

With a few quick sutures, the fish was ready for the recovery box, another cooler full of circulating seawater. Within minutes from when it was caught, Huff slid the tagged fish from his hands, back into the sea. The tag is not expected to change the behavior of the fish – in part because of its size, relative to the mass of the fish, Huff said.

The 2-year-old chinook now had an individual tracking number: 7512. Any time it’s within about third of a mile of the receiver, its travels will be logged. That’s new: a glimpse into the days in the life of a fish, live from inside 7512.

The data could revolutionize our knowledge of chinook behavior at sea.

In the past, information on where salmon travel has been largely based on coded-wire tags implanted in young fish at a hatchery, and dug out of the head of the fish as an adult when it’s caught. Such a tag tells nothing about fish that aren’t caught, or about areas where there aren’t fisheries. And nothing about what happened in between getting tagged, and getting caught. The new fish telemetry is going to help fill in some of those blanks.

Tom Quinn, 65, is a professor at the University of Washington School of Aquatic and Fishery Sciences who literally wrote the book on the behavior and ecology of Pacific salmon and trout. To him, two years of tracking data on an individual fish is an incredible bounty.

He remembers when following tagged fish around meant swigging coffee to stay awake, wearing headphones and following pings until the tags’ batteries died, within usually two days.

New battery technology has changed everything, said Quinn, aboard the Zephyr to observe the work by scientists now in the jobs he helped them prepare for in their graduate work at the UW.

Quinn has long been fascinated with the migration of salmon. From freshwater to the sea, salmon undertake a miraculous journey: “They haven’t been there before, and they are with no one who has ever been there before,” Quinn said of out-migrating salmon. “At least with birds, they can look down, and follow the adults who have been there.”

Analysis of coded wire tagging data has shown certain types of salmon from certain rivers go more or less to the same broad areas of distribution, using the earth’s magnetic field to guide them. But salmon may also have a mapped sense of the ocean, Quinn said. Even stocks raised in hatcheries and planted outside of the home rivers of their DNA still head to the “right” place in the ocean for salmon of their kind.

“They still figure it out; something sophisticated is at work,” Quinn said.

If scientists can better understand how fish disperse, and what cues they are following, they could relate that to bigger questions, such as what would happen to fish behavior under changed environmental conditions. The hope also is to scale up the array, placing receivers farther down the coast, at least past the Columbia River, with a special focus on the spring chinook so important to the whales. Arrays also are planned for the Salish Sea, including Puget Sound, working with a variety of collaborators.

As the team headed back to Neah Bay, Huff couldn’t resist checking on one of the receivers, as the Zephyr neared the array.

Captain Ron Micjan idled the boat, and Smith powered up the detector over the receiver. Relief washed over Huff’s face as the display lit up: It was 125 feet down, in 44-degree water, lying flat on the bottom, just as it should be.

And busily at work since about mid-May: “73 (fish) detections already,” Huff said. “So far, so good.”

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