Salmon study sparks controversy


Occasionally, this space includes reports and essays from guest writers on the subject of Puget Sound ecosystem recovery. Biologist and author Eric Wagner has this look at the controversy surrounding a recent study of salmon numbers in the Salish Sea. 

By Eric Wagner

A couple of weeks ago, the Canadian Journal of Fisheries and Aquatic Sciences published a research article from the Marine Mammal Research Unit at the University of British Columbia (UBC). The article, first-authored by a hydroacoustician named Mei Sato, looked at the abundance of Chinook salmon during two summers at two straits in the Salish Sea region that populations of resident killer whales frequent. In short summary, the researchers found that the Strait of Juan de Fuca (seasonal home to the southern residents) had four to six times as many Chinook salmon as Johnstone Strait (home to the northern residents).

As is now the convention when a university lab publishes a paper, the UBC news office put out a press release to tout it. “No apparent shortage of prey for southern resident killer whales in the Salish Sea during summer,” the release’s headline read.

On the surface, this whole process had been fairly straightforward and routine: conduct a study, publish the study, announce the study to the world, maybe talk about it to a local media outlet or two. But that would turn out not to be the case where Sato’s article was concerned, because when it comes to the southern resident killer whales, it’s what is going on under the surface that counts. Now, to the critical questions of how Chinook salmon abundance affects the southern residents and what to do about it, Sato and her co-authors have added a couple of more: What is more important—what an article says, or what an article about an article says?

An unexpected result

As of September 20, 2021, the southern resident population sits at 73 individuals, a number that has stayed stubbornly low despite the whales being listed as endangered under the Endangered Species Act in the United States. (In Canada, the southern residents have been protected under Species At Risk Act since 2003.)

Why the southern residents are doing so poorly is thought to be due to a suite of causes, among them pollution, vessel noise, and so on. But the main cause researchers have focused on for years is a shortage of food, especially in the late spring and summer months, when the southern residents historically come to the Salish Sea. Obligate eaters of fishes, the southern residents are known to prefer Chinook salmon, hunting them almost exclusively at times. As Chinook runs have declined throughout the region, many scientists believe the southern residents have declined with them, to the point that they are spending less and less time in the area.

Dr. Sato and a summer undergraduate student, Taryn Scarff, aboard ship surveying important foraging habitats for resident killer whales. Credit: A.W. Trites/University of British Columbia
Dr. Mei Sato and a summer undergraduate student, Taryn Scarff during a study of killer whale foraging habits. Credit: A.W. Trites/University of British Columbia

It was with that view in mind that Sato, Andrew Trites, the director of the Marine Mammal Research Unit, and Stéphane Gauthier, a research scientist with the Department of Fisheries and Oceans Canada, undertook their work. “In Canada,” says Sato, now an assistant scientist at the Woods Hole Oceanographic Institution in Massachusetts, “you always hear of the relationship between the drop of the southern residents and their prey shortage. But nobody had tested this hypothesis before.”

Chinook salmon returns are usually determined when they enter rivers on their way to spawning streams; less is known about their abundance and distribution in the larger, more open waters of the Strait of Juan de Fuca. Sato wanted to see the prey densities the southern residents face in the strait. To measure them she used multifrequency echosounders, which are akin to the fish-finders fishers mount on their vessel bottoms. Timing her surveys to when Chinook migration was at its predicted peak, she sailed out in July and August in 2018 and 2019, surveying pinch points where the salmon were likely to be funneled. So she could compare whatever she found in the Strait of Juan de Fuca with other orca waters, Sato also did surveys in the Johnstone Strait.

The northern resident killer whales that spend the summers in Johnstone Strait number about three hundred animals. The population is generally understood to be much healthier than the southern residents. Sato thus thought she would see a bounty of salmon in Johnstone Strait and peanuts in the Strait of Juan de Fuca. Instead, she saw the opposite: while Chinook salmon were patchily distributed and of similar size in both straits, the patches in the Strait of Juan de Fuca had four to six times as many Chinook as those in Johnstone Strait.

“We didn’t expect this result at all,” Sato says. “We came in believing the food hypothesis too.” But the numbers were the numbers. As she and her co-authors wrote at the close of their paper, “This suggests that other factors such as spatial and temporal mismatches between killer whales and prey presence, shortages of prey outside of the Salish Sea, reduced energy content of individual Chinook salmon, and reduced prey accessibility due to vessel traffic may be more consequential to southern resident killer whales than previously considered.”

To say that the results were controversial is an understatement. Two days after the paper’s release, a consortium of scientists who study the southern residents, headed by Monika Wieland Shields of the Orca Behavior Institute, released a strong critique. “The new paper by Sato et al. describes a new methodology for surveying for Chinook salmon in the oceanic environment,” the scientists wrote, “but includes too many unknowns and is too small of a data set to come to such a broad-sweeping conclusion.”

Photograph of a group of Southern Resident killer whales chasing a salmon, collected during health research with a drone flying non-invasively at srcset=
100ft. Credit: Holly Fearnbach from SeaLife Response, Rehabilitation and Research (SR3), John Durban, formerly with NOAA Southwest Fisheries Science Center, and Lance Barrett-Lennard from the Ocean Wise Research Institute. Research authorized by NMFS permit #19091.” width=”300″ height=”225″> Photograph of a group of Southern Resident killer whales chasing a salmon. Photo courtesy of NOAA. Research authorized by NMFS permit #19091.

Whale researchers responding in the press were even more critical. “They are making a lot of assumptions and my concern is that once you stitch all those assumptions together, you can end up with an answer that is incorrect,” Brad Hanson, a biologist at NOAA, told the Seattle Times. Others were even less inclined to be polite. Ken Balcolm of the Center for Whale Research called the paper “a nice little fish thing,” while Deborah Giles, a biologist at the University of Washington and research director for Wild Orca, told the Times, “To say the southern residents are getting four to six times as much salmon as the northern residents is just silly. And here we are, trying to find a nice way to say that.”

Parsing the reactions

Here, though, it becomes necessary to parse whether the killer whale research community was reacting to the paper or to the press release about the paper. The release says the UBC researchers “debunked” the hypothesis that southern residents are facing a food shortage. Sato and Trites say they make no such claim; they don’t dispute that the southern residents are showing up thin, or that Chinook populations are in general decreasing. “Just because we found that there are more salmon in the Strait of Juan de Fuca doesn’t mean the killer whales necessarily have access to those salmon,” Trites says. “We didn’t look at interference from vessels, or underwater noise, or things like that.”

When asked about the science the paper itself describes, Shields, the author of the critique, is more measured. “It was a novel application of technology for how we survey salmon in the ocean,” she says. “I thought that was fascinating and super cool.” Her concern was more with the way the science became embellished during promotion. “As advocacy groups and marine educators we work very hard to get correct information to the public. One of the messages the research community has supported is that this is a prey-limited species. For the headline to be Prey’s not a problem here anymore! deflects from a really big issue that we need to focus on.”

Hanson echoed this when he told the Times he was worried the findings could be “weaponized” by parties with an interest in promoting more fishing, or aquaculture practices blamed for playing a part in declining salmon returns. At least one online publication has used the findings to attack other research on Chinook declines. “Anti-salmon farm activists have long been trying to link the apparent lack of Chinook salmon prey for British Columbia’s resident killer whales to the region’s marine aquaculture operations,” pronounced SeaWest News, a publication run by a self-described media agency with clients from British Columbia’s seafood industry. “But that theory, like many others trotted out by the activists, has been debunked by a new study led by scientists at the University of British Columbia,” the article said.

Trites approved the press release before it went out, “but in retrospect I shouldn’t have, given how muddled things have gotten.” Some of the vitriol and derision in the responses took him aback. “People should focus on the science,” he says, “rather than try to infer motive.” Although he expected the paper to make waves because it questions an orthodoxy, he shares the concern that the results could be misinterpreted or, worse, misapplied. “I can tell you one thing,” he says. “When we get a result we don’t expect, we dig really hard, we look under every little rock.” He feels the paper’s message is getting lost a little in the fuss over the press release, which has become a sort of object-lesson in how, in trying to amplify a scientific result, the result is instead obscured, and commenting on it becomes a professional game of Telephone.

“To me, the take-home isn’t about whether or not there’s a food shortage, it’s about where the food shortage is occurring,” Trites says. “Everyone is focused on the Salish Sea, but the southern residents are only here part of the time, and they need food every day of the year. What we want this paper to do is get people to ask whether there are sufficient prey to support southern resident killer whales during winter and spring when they are south of here. The conversation needs to go beyond the Salish Sea if we are going to save the southern resident killer whales from extinction.”

Eric Wagner writes about science and the environment from his home in Seattle, where he lives with his wife and daughter. His writing has appeared in Smithsonian, Orion, The Atlantic and High Country News, among other places. He is the author of “Penguins in the Desert” and co-author of “Once and Future River: Reclaiming the Duwamish.” His most recent book is “After the Blast: The Ecological recovery of Mount St. Helens,” published in 2020 by University of Washington Press. He holds a PhD in Biology from the University of Washington.