Researchers in the state of B.C. salmon in hot water blob – Terrace Standard


An anomaly or new standard, researchers are closely following the lingering bubble of warm water in the northeast Pacific Ocean and what that means for salmon.

In the last two months, a high pressure ridge that developed over the coastal area of ​​B.C. resulted in a prolonged hot summer. The storm season was late and the water is between two and three degrees warmer.

Richard Dewey, associate director of science at Ocean Networks Canada, and the University of Victoria, carefully monitored the approximately 2,000-kilometer area of ​​exceptional temperature that first appeared in the fall of 2013 and became much more remarkable in the spring of 2014 – when researchers coined the term "the blob."

"This event has woken us up to what is happening here. The atmosphere, storms and jet streams come together and we have weaker winds on the gulf and therefore we do not mix the cold water and things stay warm, "Dewey said.

Now they are paying attention. In 2017, oceanographers began to see the hot mass dissipate in depth, but this year it is back in the Pacific Northwest and the Bering Sea.

"Maybe this is the trend. Maybe that's how climate change is going to be reflected in our backyard, but we still do not know that, "Dewey said.

Ocean Networks Canada has instruments along the bottom and near the ocean shore. They did not catch the 2014 bubble in their sensor until months later, so researchers are closely monitoring satellite data and sea surface temperature maps in the Gulf of Alaska.

Impacts on salmon

Warming of the ocean is also affecting freshwater temperature.

Sue Grant is leading the Fisheries and Oceans Canada Salmon Status Program (DFO). Its role is to integrate what we know about salmon and its ecosystems. Oceanographers and freshwater researchers are seeing a correlation between the bubble and the warming in rivers and streams.

"The blob itself is an oceanographic phenomenon, but it is caused by a coupling with the atmosphere and this also has repercussions on fresh water," Grant said.

Salmon are anadromous, with freshwater and marine life stages, and they are experiencing warmer temperatures in both habitats. Grant said that the effects of the 2014 and 2015 tepid bubble vary between salmon stocks in B.C. and Yukon territory.

"The responses are mixed, although some of our southern stocks and some of our northern ones were not doing so well this year. We were seeing a survival rate lower than the average salmon stocks in the Fraser watershed last year in different species, and we were seeing the below average survival rate again this year at Fraser. There are other examples in the north, "she said.

Grant uses a marathon analogy to describe what temperatures above the season of 3 to 5 degrees Celsius are doing with salmon.

If she runs a 50 degree Celsius marathon, she may not survive because 50-60 degrees Celsius is outside her ideal temperature range. Salmon also has an ideal range of temperature, and when it tries to migrate upstream during the summer season, it may adversely affect its migration.

Water temperatures above average are also affecting the nutrient level.

When the ecosystem changed in 2014-2015, the surface layer of the Alaskan Gulf was weaker in nutrients. Ocean Networks Canada noted that cold water species requiring a nutrient rich environment were not as common, while hot water species that adapted to low nutrient conditions tended to dominate.

"When the salmon is out there in the gulf and along the coast feeding under these conditions, it returned in 2016-17, a bit smaller than usual," Dewey said.

"The numbers I've seen say that these hot conditions can result in smaller sizes of fish, which also has some impact."

Grant and Dewey say they are paying attention, but it is still too early to make projections and what the hot bubble of 2018 means for salmon.

They can, however, pick up the data from the past few years – salmon responses to freshwater and marine ecosystems – and see if there is a pattern and what that might mean for the future of salmon stocks.

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