The international salmon expedition will try to find out why so many salmon go out into the Pacific Ocean and never return.
By Christopher Dunagan
An international team of 21 scientists will embark Sunday on a wintry expedition that could help untangle some of the greatest mysteries surrounding Pacific salmon: Where do these migrating fish go when they leave their local waters, and why are they dying in such large numbers?
Biologists, oceanographers and other specialists from five countries will travel into the rough waters of the Pacific Ocean during the winter in search of six species of salmon, as well as the prey they eat and the predators that would eat them.
The Russian research vessel, named Professor Kaganovsky, will traverse about 6,000 miles in a back-and-forth pattern, catching and studying marine creatures over an estimated 345,000 square miles of the ocean, including the Gulf of Alaska and areas off the coasts of British Columbia and Washington.
“Nothing like this has ever been done before, considering the breadth of work we will be doing in the Gulf of Alaska in the winter,” said Dick Beamish, a longtime salmon researcher in Canada who conceived of the expedition and raised about $1 million to fund the voyage. The long-anticipated expedition is part of this year’s International Year of the Salmon.
“After 100 years of research, we know a lot about Pacific salmon,” Beamish noted, “but most of what we need to know, we don’t know. We want to understand the mechanism of what regulates abundance.”
Numbers alone don’t tell the story. Fifty years ago, about 5 percent of the chinook salmon that left the streams returned as adults, and that meant plenty of salmon for harvest and spawning. Today, if 1 percent comes back it’s a pretty good year. But so far nobody really knows what happens to the salmon that disappear into the ocean — often called the “black box” of salmon mortality — nor do they know why more chinook are dying today than ever before.
[Read our 2018 series “Opening the black box: What is killing Puget Sound’s salmon and steelhead” in the Encyclopedia of Puget Sound.]
“I think all of us accept the idea that we are changing our ocean ecosystems,” Beamish said.
In a 2001 research paper, Beamish and Conrad Mahnken of NOAA Fisheries hypothesized that most of the young fish entering the ocean died during their first year. Those that grow the fastest survive the best, they suggested. Smaller fish are more likely to fall prey to larger fish, they said, and those that fail to build up enough energy reserves for winter will become less fit and more vulnerable when food becomes scarce.
The expedition, intentionally scheduled for this time of year, will be able to take a close look at the young fish that have survived so far, said Laurie Weitkamp, a salmon biologist with NOAA’s Northwest Fisheries Science Center in Newport, Ore.
“We expect to see a lot of skinny fish with empty stomachs,” said Weitkamp, one of three chief scientists on board the research ship. “It might be a time when they start feeding again.”
Experts hope to sample the entire food web — from the variety of plankton that feed the smaller fish to the salmon sharks (Lamna ditropis) that can make a meal of the adult salmon. By estimating the total number of each species in the ocean, the researchers hope to describe why some species do better than others, and possibly estimate the “carrying capacity” of the Gulf of Alaska.
The research ship will tow a variety of plankton nets to sample the tiny creatures as well as a midwater trawl net that can catch fish and other marine animals down to about 160 feet.
Looking at the survivors near the end of winter and analyzing their genetic makeup may help researchers draw conclusions about the traits that give them an advantage, Weitkamp said. “Were they just in the right place at the right time, or are they the Michael Jordans of the salmon world?”
The nets will also catch adult salmon, including those getting ready to return to inland waters and their home streams. That information should help to more accurately forecast the size of the various salmon runs returning this summer and fall.
By checking the scales of the fish and their ear bones, called otoliths, the researchers will be able to tell the ages of each fish. Otoliths can also reveal the rate of growth through each stage of a salmon’s life.
Through DNA sampling, researchers will have a good idea about the origins of all the salmon caught during the expedition. Based on the time and location, they expect to find more pink and chum salmon than any other salmon species.
The expedition could directly confirm previous findings that chinook salmon from Alaska tend to stay in the Gulf of Alaska, while Puget Sound stocks move slightly north and west into deep water west of Vancouver Island. Measurements of temperature, salinity, prey type and abundance, along with other factors could reveal why some areas are preferred over others.
“The different stocks all use the ocean differently,” Weitkamp said. “If you are only catching southern stocks to the south and northern stocks to the north, is it a temperature preference or is it possibly where there is a lot of prey?”
The expedition might tell something about competition between hatchery and wild fish as well as other effects that hatchery fish may have on the food web.
Besides examining the DNA of salmon caught during the cruise, advanced “environmental DNA” techniques will be used to check water samples for a full list of other species that may be present in a given area.
Some of the fish caught during the expedition will be released after being implanted with tiny instruments to measure water conditions while tracking their route of travel. Those fish will be tagged with an external disc, in hopes that someone will find and return the fish for data recovery.
The concept of building an international team of scientists to study salmon was promoted in a 2009 paper written by Beamish, Brian Riddell of the Pacific Salmon Foundation and 35 others. The paper argued that important discoveries are more likely to be accomplished by unifying the expertise of the five major salmon-producing countries in the North Pacific.
Beamish learned that he could charter the best Russian research ship and crew, which are experienced in winter fishing and taking scientific measurements under grueling high-seas conditions. By stressing the importance of the voyage and international cooperation, Beamish has been able to raise more than $1 million, including contributions from the Canadian federal government, British Columbia government, Pacific Salmon Commission, Pacific Salmon Foundation, British Columbia Salmon Farmers Association, Sitka Foundation, Harmac Pacific paper company and others.
He has also enlisted an experienced team of researchers — including 10 Russians, six Canadians, three Americans, one Japanese and one Korean, who will live together in close quarters for the next month, sharing their lifelong findings and ideas. The expedition leaves Sunday from Vancouver, B.C.
“Everybody knows that this is not going to be a luxury cruise,” Beamish noted. “These people have agreed to go out into the Gulf of Alaska in the winter, and they know they are going to get seasick.”
A powerful attraction is the chance to make first-time observations with implications for short- and long-term salmon survival, Beamish said, adding, “It is likely that we will make discoveries that will change how we do salmon research in the future.”