Wildlife officials say the heat wave is expected to kill all juvenile Chinook salmon in the Sacramento River in California. At the same time, climate change and extreme heat waves have also hit salmon on both sides of Canada.

So, how bad is it here, and what can we do to save our salmon? CBC News explained.

What happened to California salmon?

California Department of Fish and Wildlife Warning last week Among the Chinook salmon in the Sacramento River, “it is possible that all Hanoi juvenile fish will not survive this season.” This is due to the heat wave pushing the local temperature above 37 degrees Celsius, and the drought caused more water to flow. Cities and farmers have caused the river to become shallow and rapidly heat up.

Does this kind of thing happen further north?

There are some reports that it happened this year Record-breaking heat wave in British Columbia The BC Wildlife Federation reported that the temperature of the Okanagan River exceeded 23 degrees Celsius this week, causing sockeye salmon to stop migrating.

“This run is very likely… destroyed by the heat,” said Jesse Zeman, the head of the federation’s fish and wildlife recovery program.

In 2016, warm temperatures were blamed on Return the minimum number of sockeye salmon Recorded in the Fraser River in British Columbia. Two years later, officials warned that the river So warm that migrating sockeye salmon may die In their journey. In 2019, there was a salmon death related to high temperature In alaska and In a fish farm in Newfoundland.

Watch | The team investigates dead salmon on the Alaska River:

In July, a team from the Yukon River Inter-Tribal Fish Commission in Alaska investigated dead salmon on the Koyukuk River. 2:18

But salmon deaths due to high temperatures are not necessarily sudden and noticeable. Many populations of Pacific and Atlantic salmon have been declining for decades, and scientists say that rising temperatures and other aspects of climate change have played a role.

How can warm temperatures harm or kill salmon?

Atlantic salmon and Pacific salmon are cold-water fish, which means that they tend to perform best in teenage temperatures, and struggle above 20 degrees Celsius.

Warm water can harm salmon in many ways. On the one hand, warm water contains less oxygen, making it harder for fish to breathe. Because they are cold-blooded animals, when the environment becomes too hot or too cold, they cannot adjust their body temperature relative to the environment. Warm temperature will accelerate their metabolism, causing them to need more oxygen and food, and also forcing them to swim to cooler waters and consume more energy.

Scott Scott, head of the salmon project at the Canadian Department of Fisheries and Oceans, said high temperatures make it more difficult for them to swim and put pressure on salmon to migrate to their spawning grounds. As a result, some are unable to survive to lay eggs, and those who survive offspring may produce unhealthy offspring.

Will other effects harm salmon?

Yes. In addition to extreme heat, climate change has also led to drier weather. Aaron Hill, executive director of the Watershed Observation Salmon Association, said that shrinking glaciers, smaller snow in winter and early melting in spring have reduced the amount and depth of water in rivers, causing them to heat up faster.

“At the end of summer, the river water level becomes low and it becomes very hot for salmon,” he said.

Watch | British Columbia glaciers are melting at an alarming rate”

Chris Brown reports that the hot summer is a “window of sorrow” to the future without glaciers 10:23

During droughts, humans will also transfer more water to cities and farmers, while leaving less water in the rivers-this is a big problem for the Sacramento River in California, and it is also a water-stressed area in British Columbia, such as Inland and east coast of Vancouver Island.

Hill said people have also absorbed too much groundwater, which would otherwise cool the stream as it gradually seeps into it.

Pests such as deforestation, mountain pine beetles, and logging caused by wildfires have increased erosion and landslides, which may damage spawning grounds or prevent salmon from migrating to these spawning grounds.

Hill said: “This is just a series of complex and interactive effects caused by nature and man.”

But salmon not only face challenges in the river, because they spend most of their lives at sea.There they also face Ocean heat waves, such as heat waves called “lumps”, Grant said that from 2013 to the present, the temperature on the Pacific coast has risen by 3 to 5 degrees Celsius. This changed the food web, replacing the fatty northern zooplankton normally eaten by salmon, and the lower nutritional value of zooplankton in the south.

“Animals that feed on these inferior animals at the bottom of the food web will grow more slowly,” Grant said. “They will be more vulnerable to predation.”

Watch | How a new “spot” will affect marine life on the coast of British Columbia:

Officials say a new ocean heat wave has spread to a part of the Pacific Ocean off the coast of British Columbia. So far, it has developed into one of the biggest heat waves in the past four years, second only to the infamous “clump.” Marine life five years ago. 7:10

Atlantic salmon face a similar impact in the northwestern Atlantic, with fish from all populations in North America and Europe growing into adults.

“This has had a major impact on ocean survival,” Crabbe said, noting that since the early 1990s, fewer adults have returned to Canada to lay eggs.

Are all salmon vulnerable?

Some people are more vulnerable than others. On the Pacific coast, Chinook’s situation is particularly bad. Decline in number, size, and reproduction rate Within their scope, from California to Alaska, Grant said he was a 2019 report Regarding the performance of Pacific Salmon.

Pink and chum are short-lived species in fresh water, where temperature changes are more extreme, and they perform better than Chinook, coho and sockeye. Grant stated that after the report was released, Pink and Confidant did experience some decline in 2019 and 2020.

Saw spawning sockeye salmon, a Pacific salmon, along the upper reaches of the Adams River. Chinook, coho salmon, and sockeye salmon spend longer in freshwater, and because pink and close friends spend more time at sea, their decline is greater. (Jonathan Hayward/Canada Press)

Emily Corey, a PhD student at the University of New Brunswick, has been studying the effects of heat stress on Atlantic salmon juveniles. She said that Atlantic salmon juveniles are particularly vulnerable.

She pointed out three main reasons why young people face greater risks:

  • They spend the first three to five years of their lives in fresh water, where the temperature will become more extreme.
  • They can’t swim.
  • They are often territories, so they don’t like moving to a new place unless they have to.

In other words, her research found that if necessary, some people can travel several kilometers to find cold water.

What measures are being taken to reduce the impact of extreme heat on salmon?

In June, the federal government Announced a $647.1 million Pacific Salmon Strategic PlanIt includes multiple solutions, also for Atlantic salmon:

Protection and management

This involves habitat monitoring and restoration, some objectives of the Watershed Observing Salmon Association and the Atlantic Salmon Federation and their partners.

In Nova Scotia, the Margaree Salmon Association installed water temperature monitors in the Margaree and Mabout rivers to help find hot spots. When they are found, the staff will do some things, such as planting trees to shade these places.

In New Brunswick, the Miramichi Salmon Association has Strengthen the cold pool Carve them out and make them bigger by following the river through the diverging river.

The Donnelly Creek Cold Water Enhancement Project was completed in 2014 by the Miramichi Salmon Association. It is designed to guide the flow of water to expand the cold pool in the waterway, where salmon can escape the heat. (Nathan Wilbur/Atlantic Salmon Federation)

On these two coasts, environmentalists say that better land use planning and protection and reforestation of salmon habitat will have a major impact. In New Brunswick, ASF is working with the provincial government to protect the most critical cold water springs and streams that flow into important salmon rivers, such as the Miramichi River.

In British Columbia, Hill said there are large areas of potential salmon habitat throughout the Fraser River Basin that have been blocked by structures such as culverts and road intersections. They can be replaced with alternatives that allow salmon to use the habitat.

At the same time, in drier areas, Hill stated that better water resources planning is needed, as well as permitting and regulating groundwater use, but the provincial government has not yet implemented it.

Changes in fisheries and harvests, closures

This is what happened on both coasts. In late June, the federal government Closed 60% of the commercial salmon fishery In BC and Yukon, to keep inventory. Most recreational fisheries in Fraser chinook also have Facing widespread closures since 2019.

Many commercial Atlantic salmon fisheries have also been closed. In 2018, the Atlantic Salmon Federation reached a 12-year agreement with partners in Iceland and Greenland. Prohibition of commercial fishing On the west coast of Greenland and the Faroe Islands. Crabbe said it appears that more salmon have returned to Canada.

Watch | More Atlantic salmon returned from the ocean last year

Biologists found a silver lining in the year when Atlantic salmon populations increased. 3:49

Crabbe added that when the water temperature exceeds 20 degrees Celsius, the important cold pool in the NB Miramichi River system usually prohibits recreational fishing. In 2018, such days will be nearly 60 days.

Stocking plan. Increasing hatchery production is one of the solutions to the Federal Pacific Salmon Strategy. In California, officials’ goal is to save the Sacramento Chinook by trucking them to the hatchery. Hill said there are desperate situations that require this kind of response.But in general, this is controversial because there is evidence that salmon farmed in hatcheries is Less suitable for survival than wild animals.

Will salmon go extinct due to climate change?

“No one is worried that they will disappear,” Grant said.

They do seem to have adapted to climate change to some extent. Both Atlantic and Pacific salmon are found further north, and some northern salmon populations are in good condition. But both Crabbe and Grant said that some populations may disappear, especially in the south, and communities with deep and close ties to salmon will feel the loss.

Grant said: “They are really important for food, social, and ritual reasons. They are very important to the aboriginals of Western Canada, and they really play an important role in the fishing industry.” “They are integrated into the culture… This may be true for all Canadians.


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