Yukon/Alaska Salmon Shrinking In Size, Producing Fewer Eggs Across Multiple Species

[hatrack]

Back in the 1970s, Peggy Kormendy recalls pulling an 84-pound chinook salmon from the Yukon River. It was a massive haul, a once in-a-lifetime event that’s probably going to become even less likely from here on out. Salmon were just bigger and healthier then, the Tr’ondëk Hwëch’in First Nation Elder told The Narwhal. Now salmon tend to be about 10 to 15 pounds. “When we were fishing, they were in good shape,” Kormendy said. “Then, the fish were getting smaller … I don’t know why.”

Recent research comes closer to an explanation. Four species of salmon are indeed getting smaller, largely a result of them spawning at a much younger age, according to a joint study conducted by researchers at McGill University and U.S. schools and government departments.

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Peter Westley, co-author and researcher at the University of Alaska Fairbanks, said this work bolsters what Indigenous people have observed. “There’s agreement, there’s no question: the fish are much, much smaller,” he said. Chinook salmon in particular, Westley continued, have taken the biggest hit in Yukon, declining in size by nearly 20 per cent in some areas over just a few decades.

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Researchers focused on four species of Pacific salmon — chinook, chum, coho and sockeye — and found that each were smaller in size after 2010 than those observed before 1990. There were patterns for species across several regions, the study says, noting that chinook salmon decreased in length by an average of eight per cent, the greatest rate of decline compared to other species. That decrease jumped to 10 per cent in the Yukon River system in particular. (Female chinook salmon now produce 16 per cent less eggs on average — a troubling result for the dwindling chinook population.)

As well, coho decreased in length by 3.3. per cent, chum were 2.4 per cent smaller and sockeye saw a 2.1 per cent decrease in length. In order to calculate the change in salmon sizes, researchers parsed through six decades’ worth of size and age data for 12.5 million salmon, collected by the Alaska Department of Fish and Game.

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https://thenarwhal.ca/yukon-alaska-salmon-declining-size/

[secondwind]

1. Climate change?

[2naSalit]

2. And pollution among other man-made fish killing

substances and practices.

[Boomer]

3. That's a broad brush

How specifically does climate change come into play?

I can think of several different possibilities. Change in water temperature could affect growth patterns. But even more likely is just the paucity of food -- ocean populations of krill are dropping and food chains are collapsing. That's not all exclusively related to climate change, however; overfishing is also destabilizing the ocean ecosystem, as is exposure to microplastics.