Tracking salmon abundance in the Pacific Ocean

As salmon populations continue to decline across the Central Coast and beyond, researchers are looking to the open ocean to help understand salmon survival dynamics.

Salmon are a “keystone species” within BC’s coastal ecosystems—a critical food source for many land and marine species, and vital part of the culture, social structures and economies of Central Coast Nations.

For years, salmon populations have been in decline, leading to profound negative impacts on other species, such as orcas and bears, and on the fisheries that remain so important for coastal communities—including food, social or ceremonial (FSC), commercial and recreational fisheries. To help seek answers, Tristan Blaine, CCIRA Field Technician, was asked to join an international research expedition far off the Central Coast—in hopes of learning more about the dynamics of salmon growth and survival in the open ocean, and reporting back to Nations.

Chum salmon returns to Kynoch to spawn. Photo by Tristan Blaine.

The expedition

Led by world-renowned Canadian scientists Richard Beamish and Brian Riddell, the late-winter expedition (March 11 to April 7, 2020) was a follow-up to the first winter research trip undertaken in 2019. “We have a lot of data on salmon in their coastal phase of life, but so much of their life cycle is spent offshore,” says Tristan. “This research aims to learn what’s happening in the ocean that may be affecting salmon stocks.”

In his online presentation providing a recap of the trip, Tristan first described some of the trials that can often hinder such a long journey out at sea. “Lots of bad weather and nine-metre swells; some sleep deprivation and seasickness,” he recalled with a laugh. “We were hauling in a load of fish every seven hours, which meant working around the clock, collecting data on the health, diet and stock identification of each salmon. Plus, of course, there was a pandemic to contend with.”

Members of the international team not only spoke different languages, they also had different ways of doing their jobs. “If we hauled in a load of fish, there was no time to wait; we had to analyze it right away,” says Tristan. “Eventually, we found ways to work together effectively and merge our different methodologies. It was a great example of people working together to do the best science in the world.”

The science team sorting and tagging salmon while the fishing crew preps for another trawl. Photo by Tristan Blaine.

The two expeditions are the first comprehensive attempt at understanding the factors that impact Pacific salmon in winter—the least studied period in the species’ life history, yet a time that many believe may strongly affect their abundance. The unprecedented research effort—part of the International Year of the Salmon initiative—covered a vast area (more than 600,000 square kilometres), and will help to identify mechanisms affecting salmon survival in the face of changing ocean conditions due to climate change and many other factors related to food production.

After Tristan’s overview, Brian Riddell provided some more detail on the motivations for the expedition and the straightforward questions that drove their research: Is the first winter at sea a major determinant of salmon production? And if so, what can we learn about these dynamics to improve salmon forecasts of future returns in coastal waters and communities?

Having worked for decades on salmon research and conservation initiatives, Brian was the past President and CEO of the Pacific Salmon Foundation, and continues to be a Science Advisor, and also a Canadian Commissioner to the Pacific Salmon Commission. He says fish that grow faster in the first months at sea are more likely to survive the winter than smaller fish, which explains the team’s hypothesis, that adult salmon abundance is strongly influenced by survival of juvenile salmon at the end of their first ocean winter.

Brian says it’s still too early to say with certainty that winter growth and survival conditions in the open ocean determine adult abundance of Pacific salmon. “Most of our data remains to be analyzed,” he says, adding that it’s critical to continue these studies if we hope to increase accuracy of forecasts. “We believe this can be accomplished,” he says, “but it will require additional years of effort and more surveys than a single vessel in millions of square kilometres of ocean.”

Juvenile chinook at the Percy Walkus Hatchery, Wuikinuxv Territory. Photo by Billie Johnson.

Takeaway and next steps?

The researchers will continue to analyze the samples and data collected, looking to produce a more detailed final report linking oceanographic data to what they learned about salmon life in the open ocean. However, these efforts have been significantly delayed by COVID-19. The scientists are already looking into future surveys that would provide more data and more clarity; they say the open ocean surveys over the past two years highlight the need for more global research in identifying mechanisms that affect salmon populations in the Pacific.

For Central Coast Nations, these surveys could be highly useful in tandem with the salmon counts and surveys undertaken along coastal streams every year.

Expected open ocean ranges for Pacific Salmon species and the 2020 study area. Map by CDEdwards Mapping.

Posted by CCIRA