Apparently fueled by a warming Bering Sea, the 2019 salmon boom in Northwest Alaska stretched far to the east along the Arctic Coast.
Canadian officials are reporting they saw unprecedented numbers of salmon in their waters east of the Alaska border.
“The salmon frenzy that started in the western Arctic earlier this year has gone on to reach a historic high,” the CBC reported Monday. “Karen Dunmall, a biologist with Fisheries and Oceans Canada, said they got more salmon from harvesters in the western Arctic and Nunavut this year than in the last 20 years combined.”
As in Alaska, most of the salmon were chums, but Dunmall told the CBC that “starting in 2004, pink salmon started showing up in the even amount of years … (and) more recently in 2016 and ’17, sockeye appeared.”
A big-run phenomenon swept north this year from the Aleutian Islands along both coasts of the Bering Sea and then east into Canada and likely west into Russia, although there is little reporting about what goes on along Russian’s Arctic coast.
What is known, according to the McDowell Group, a consultancy, is that Russia harvested about a billion pounds of Pacific salmon this year – 60 percent of the fish being pinks – in a year when pink runs are traditionally weak along the Kamchatka Peninsula.
That’s about 200 million pounds more than the averaged annual harvest for Alaska in 2018-19, McDowell reported. The 2018 Alaska harvest of 114 million, though good by historical standards, was weak by modern standards.
The good now days
Bristol Bay, the easternmost arm of the Bering, was the focal point. The harvest of 44.5
million salmon of all species was the second largest in Bay history and resulted in a record payment to fishermen of nearly $307 million, according to the Alaska Department of Fish and Game.
More than 90 percent of the catch by weight was high-value sockeye trading at $1.35 per pound, according to the state agency.
The Bay’s sockeye, according to the University of Washington scientists, are so far proving to be one the big winners in a warming North Pacific Ocean. The 2019 harvest of 43 million of the fish was 76 percent above the 20-year average catch, according to Fish and Game.
“We know climate warming is making rivers more productive for the food juvenile salmon eat, meaning their growth rate is speeding up. That puts the salmon on a growth trajectory that moves them to the ocean faster,” University of Washington (UW) scientist Daniel Schindler told the UW News after he and colleagues published on sockeye growth rates in Nature Ecology & Evolution last year.
Plankton production in the region’s lakes has gone up as they have warmed. Young sockeye feed on that plankton. As a result, they grow faster and bigger and go to sea sooner, which tends to take some of the bite out of the historically high death rate for salmon.
About 90 percent of the young salmon that survive a year or two in freshwater before going to sea die in the ocean. With hundreds of millions of young fish going to sea, however, even a percent change in how many come back can make a big difference in the size of returns.
Scientists studying California salmon earlier this month reported finding big shifts in growth rates in young salmon as waters warm thus helping the fish grow faster and bigger. That increases their survival chances at sea.
Those researchers concluded “abundant food sources may help buffer the effects of increasing water temperature,” according to a report from the University of California Davis.
“The study, published in the Canadian Journal of Fisheries and Aquatic Sciences Dec. 10, shows that the availability of food in a natural system – not just stream temperature and flows – is an essential component of fish habitat,” the university reported.
The study is in keeping with the metabolic theory, which basically holds that the biological carrying capacities of warm waters are higher than those of cold waters, but the California scientists said they were still surprised by what their examination of coho salmon revealed.
The optimum water temperature for young coho salmon has long been thought to be in the mid-50s, but UC Davis reported “the researchers were surprised to find that coho salmon growth rates peaked at average water temperatures of 61.8 F and an ‘unheard of’ maximum weekly temperature of 70 degrees.”
Because salmon are cold blooded, their body temperatures rise or fall with water temperatures. When the water warms up, they warm up, and their metabolism increases accordingly.
The higher metabolism increases their need for food. If food is lacking they are in trouble, but if food is available, the warmer water just helps them grow faster.
The California scientists reported young fish reared in water with a mean temperature of 61.8 degrees and a peak weekly temperature of 70 degrees gained 9 grams on fish reared at 55.4 degrees with a peak weekly temperature of 60.8 degrees.
The results are similar to those being seen in the Bay as water temperatures rise in area lakes, and scientists say it is likely the salmon boom along the Arctic coast is similarly tied to warming.
“So the salmon are responding to environmental variability and change,” Dunmall told the CBC. “Generally, things are warming up.”
The biggest increases in global warming are being seen in the Arctic. It is warming at about twice the rate of the rest of the planet as sea ice melts away, according to the National Aeronautics and Space Administration (NASA).