Climate change and sockeye salmon don't mix

In west coast rivers, the carcasses of salmon that die after spawning literally feed nearby forests and the animals that live there. One study even shows that you can see from space the impact of salmon on the greenness of trees along waterways. But repeated episodes of heat and drought could change the situation.

A sockeye salmon in the Adams River.

Every four years, the Adams River, in British Columbia, is the scene of an unparalleled run of sockeye salmon. They are normally millions to return to reproduce in the same place where they were born and where they will die.

But in early October 2022, the long-awaited performance did not go as planned. The most famous of all Pacific salmonids was not there.

It's super worrying because we should have seen a huge amount of salmon coming back, like it normally happens every four years, says Professor John Reynolds, head of the Terrestrial and Aquatic Conservation Laboratory at Simon Fraser University.

John Reynolds, head of the Terrestrial and Aquatic Conservation Laboratory at Simon Fraser University.

For weeks, British Columbia broke heat records and there was no rain. River levels remained very low and water temperatures high.

Unheard of for the organizers of the Salut au sockeye festival. Barely a few salmon have arrived in the Adams River, as if it were the height of summer, says guide Ted Danyluk.

“We are the October 1, sitting here in a t-shirt. People are by the river in sandals. This is not normal. Autumn is long overdue.

—Ted Danyluk, Guide, Adams River Salmon Society

The migration of millions of sockeye salmon is central to the life of the Secwepemc First Nation. Its members have been meeting since the dawn of time on the banks of the Adams River to celebrate their return in the fall.

Dawn Francois, Little Shuswap Lake First Nation

Councillor Dawn Francois makes a sad statement today.

“When I was little, the river was red with salmon, there were so many! We could have crossed it simply by walking on their backs. And look today, there is practically nothing left.

— Dawn Francois, Little Shuswap Lake First Nation

She is increasingly concerned about the impact of climate change on sockeye populations.

Salmon is an integral part of our culture, our rituals and the whole ecosystem. Without salmon, we would not have survived the winters. It keeps us alive, like all species on Earth, she adds.

“And if the salmon disappear, what will happen to us?

— Dawn Francois, Little Shuswap Lake First Nation

The impact of climate change is also of concern to John Reynolds. The most recently chair of the Committee on the Status of Endangered Wildlife in Canada notes that the last 10 or 15 years have been difficult for salmon in southern British Columbia.

The 2010 large Adams River run was exceptional with the return of approximately 3.8 million sockeyes. In 2014 only 707,000 returned, and in 2018 that number dropped to 535,000 sockeye.

“It's a cold-water fish, and we now know that warming oceans are having a negative impact on it. So, it must not only survive and manage to develop sufficiently at sea, but now there is the problem of water temperature when it comes time to go up the river.

— John Reynolds, head of the Terrestrial and Aquatic Conservation Laboratory at Simon Fraser University

For the sockeyes, the upstream becomes extremely difficult when you combine a low level of the river with a water temperature that rises above 20 degrees Celsius.

We are very concerned about what is happening in the Adams River. Even if things are going badly in some parts of the world, here, we could always celebrate, every four years, this beautiful big run of salmon. So what's happening this year is making me pretty anxious, says John Reynolds.

Both First Nations and scientists wonder if a decrease in the number of salmon returning to rivers will impact ecosystems.

Pacific salmon can gain up to 99% of their body mass during their stay in the ocean. They then fill up with marine nutrients, which they then bring back thousands of kilometers to the river where they were born.

“What is special about Pacific salmon is that they are programmed to die after spawning. When they go up the river, it's a one-way trip. And after, the cycle starts again »

— John Reynolds

A sockeye salmon carcass on the bed of Adams River.

By returning to die in the rivers, the salmon somehow allow the ocean to feed the forests that run along the rivers, explains the scientist.

If you take a carrot in these massive giant trees and you analyze it, you will find nutrients that come from the salmon, explains John Reynolds.

A stream runs along a riparian forest that protects against erosion.

It's not nothing. From 40% to 80% of the nitrogen found in shrubs and trees comes from the ocean.

This transfer of nutrients from fish to the forest occurs when salmon carcasses are eaten by other animals. For example, bears and wolves will carry them to shore and devour some of them. The remains then fertilize the plants.

Everything remains in the ecosystem, since the insects feed on the plants and the birds gobble up the insects, notes John Reynolds, whose studies have also shown that there are more songbirds near rivers where salmon are abundant.

Recently, John Reynolds and his team measured the impact of salmon on forest ecosystems in an original way.

The Adams River served as their model because of the millions of salmon that return to spawn there every four years. The researchers analyzed images taken from space from 1984 to 2019, a period of 36 years. They then compared them with model images to see if shades of green in vegetation were related to salmon abundance.

“It was not won! Frankly, I doubted it would be visible. But yes! After a year of great sockeye runs, the green of the trees along the river was more pronounced.

— John Reynolds

The measured increase is 1% up to 100 meters from shore. This discovery will be useful to researchers, says Celeste Kieran, co-author of the study.

Celeste Kieran, researcher, Terrestrial and Aquatic Conservation Laboratory at Simon Fraser University.

“The study highlights one of the many interactions that exist in the salmon ecosystem. It is very important to document these phenomena in order to understand how these ecosystems behave in the face of change”

— Celeste Kieran, Researcher, Terrestrial and Aquatic Conservation Laboratory, Simon Fraser University

Climate change impacts stocks Pacific salmon. (File photo)

The latest data is not encouraging. An unofficial count from Fisheries and Oceans Canada suggests that, for 2022, the return migration will not exceed 500,000 sockeyes in the Adams River. Does this mean that the huge runs of the past are now behind us?

“We will still see big runs, but the fish will come back they still by the millions? I'm not very optimistic. ”

— Ted Danyluk, guide, Adams River Salmon Society

For his part, John Reynolds believes that great challenges lie ahead and that more and more people are aware.

I remain hopeful that the sockeye will be able to surprise us. And even if we see some improvement, we must stay the course and put our protection at the top of our priorities, maintains John Reynolds.

The report by Maxime Poiré and Simon Giroux is broadcast on the show La Semaine verte on Saturday at 5 p.m. and Sunday at 12:30 p.m. on ICI TÉLÉ. At ICI RDI, it will be Sunday at 8 p.m.