Thursday , November 26 2020

Researchers on state of B.C. salmon in warm water blob – Terrace Standard

An anomaly or the new norm, researchers are carefully tracking the persistent warm water blob in the northeast of the Pacific Ocean and what it means for salmon.

In the last two months, a high pressure ridge that developed over BC's coastal area resulted in an extended warm summer. The storm season was late, and the water was two to three degrees warmer.

Richard Dewey, associate director of science at Ocean Networks Canada and the University of Victoria, has been closely following the approximately 2,000-kilometer unseasonably warm area that made its first appearance in the fall of 2013 and became much more noticeable in the spring of 2014 when researchers coined the term "the blob".

"That event woke up to what's going on here. The atmosphere, storm and jet streams come together and we get weaker winds over the gulf and so we do not mix the cold water and things remain warm, "Dewey said.

Now they're paying attention. By 2017, oceanographers were beginning to see the warm mass dissipated at depth, but this year it's back in the northeast Pacific and in the Bering Sea.

"Maybe this is the trend. Maybe this is how climate change is going to reflect itself in our backyard, but we do not quite know that yet, "Dewey said.

Ocean Networks Canada has instruments along the bottom and near the shore of the ocean. They did not pick up the 2014 blob on their sensor until months later, so researchers are keeping a close eye on satellite data and sea surface temperature maps for the Gulf of Alaska.

Impacts on salmon

Ocean warming is affecting fresh water temperatures as well.

Sue Grant is leading the Fisheries and Oceans Canada's (DFO) State of the Salmon Program. Her role is to integrate what we know about salmon and their ecosystems. Oceanographers and fresh water scientists are seeing a co-relationship between the blob and the warming in rivers and streams.

"The blob itself is a oceanographic phenomenon but it's caused by a coupling with the atmosphere and that also has repercussions in fresh water," Grant said.

Salmon is anadromous, with fresh water and marine life stages, and they experience warmer temperatures in both habitat. Grant said the effects of the 2014 and 2015 warm blob varied across the salmon stocks in B.C. and Yukon territory.

"Responses are mixed, though some of our southern stocks and some of our northern ones were not doing so well this year. We've been seeing lower than average survival rates in Fraser Watershed last year across the different species and we've been seeing lower average survivals this year in Fraser. There are other examples up north, "she said.

Grant uses a marathon analog to describe what the 3-5 degree Celsius temperature above-season is doing to salmon.

If she was to run a marathon in 50 degrees Celsius she may not survive because 50-60 degrees Celsius is outside her optimal temperature range. Salmon has an optimal temperature range as well, and when they are trying to migrate upstream during the summer run it can have a negative impact on their migration.

Warmer-than-average water temperatures also affect the level of nutrients.

When the ecosystem shifted in 2014-2015, the Gulf of Alaska was weaker in nutrients. Ocean Networks Canada saw that cold-water species requiring a nutrient-rich environment were not as prevalent, while warm-water species that could adapt to low-nutrient conditions tended to dominate.

"When the salmon was out there in the gulf and along the coast feeding under these conditions they came back in 2016-17, a little smaller than usual," Dewey said.

"The numbers I've seen say these warm conditions can result in smaller fish sizes so they have some impact as well."

Both Grant and Dewey say they're paying attention but it's too early to make projections and what the 2018 warm blob means for salmon.

They can, however, take the data from the past few years – salmon responses to the warming in freshwater and marine ecosystems – and watch for a future salmon stock.

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