Salmon origins/Ruggerone and Irvine

Alaska’s commercial fishing season has come to an end with a smallish – by decadal average standards – statewide harvest of about 114 million salmon looking almost identical to the smallish statewide harvest of 2018, which in turn looked a lot like the smallish statewide harvest of 2016.

There is clearly a pattern here. What it means, if anything, is another question.

“The Blob,” an unusual pooling of warm water in the Gulf of Alaska, got the blame for the harvest of only about 114 million salmon in 2018 as it did in 2016 when the catch was 111 million. 

There has been no mention of The Blob this year with the preliminary catch again at approximately 114 million.

And these comparatively low catches in even-numbered years have been bracketed by massive odd-year catches: 204 million salmon last year, 224 million in 2017 and 265 million in 2015.

Much of the oscillation in harvest is due to the nature of pink salmon, the smallest, least valuable and shortest-lived of the Pacific species. Odd-year and even-year pinks are genetically distinct, and in Alaska the odd-year fish are dominant in most areas.

The preliminary pink salmon harvest this year fell just short of 58 million, a little less than 45 percent of the 129.1 million catch of last year. It has long been theorized, though not proven, that odd-year pinks – or humpies as Alaskans often call them – take such a big bite out of the Gulf of Alaska food supply that even-year returns suffer for lack of food.

Less stable?

Historically, state harvests have almost always yoyoed up and down between odd and even years, but the oscillations have become greater in the 2010s. Alaska Department of Fish and Game data show that the 76 percent difference between the largest and smallest, odd-year/even-year harvests in the 1990s grew to a 145 percent difference in the 2010s.

Pink numbers have over this time been boosted by Alaska hatchery production, and there is some thought that the hatcheries pinks – along with Bristol Bay sockeye salmon – are the big beneficiaries of a warming North Pacific Ocean.

“Pinks are a boom-bust species due to their fixed life history, so their numbers will vary a lot,” said Greg Ruggerone, a Seattle-based research scientist. “Surprisingly, 2018 was the all-time biggest pink run due to the massive return to Russia.”

Ruggerone and Canadian colleague Jim Irvine in 2018 authored what is considered the definitive estimate on Pacific salmon populations. It concluded that salmon are now more abundant than at any time in recorded history.

Almost 70 percent of the adult fish were pinks with chums and sockeye trailing at 20 percent and 13 respectively, their peer-reviewed study in Marine and Coastal Fisheries said. 

“While it is good that abundance of sockeye, chum, and pink salmon is high,” Ruggerone told the American Fisheries Society at the time. “There is growing evidence that this high abundance, especially pink salmon, is impacting the offshore ecosystem of the North Pacific and Bering Sea.

“This impact may be contributing to the decline of higher trophic species of salmon such as Chinook salmon in Alaska.  Hatchery salmon are exceptionally abundant now and contribute to this impact.”

Losing value?

Outside of Bristol Bay at the southern edge of the Bering Sea in far western Alaska, high-value Chinook, coho and sockeye salmon were not plentiful in Alaskathis year. These are fish that spend one to two years in freshwater before going to sea where they may spend one to four years before returning to spawn.

Their multi-year lifestyles buffer their populations against the broad swings in numbers common to pinks, but they too have been oscillating in line with the even-odd pattern. The 2020 commercial harvest of Chinook – or kings as Alaskans call the largest of the salmon – dropped to 231,000 fish this year, according to Fish and Game data, down from 252,000 in 2018, the previous odd year and 271,000 last year.

The 2020 catch is about 70 percent of the five-year average of 328,000. The shift in Gulf of Alaska sockeye is even more dramatic. The preliminary catch of 6.1 million was less than half the five-year average of 14 million.

The Chignik River fishery on the Alaska Peninsula, once one of the most profitable commercial fisheries in the state, was a disaster, and the fabled Copper River commercial fishery south of the state’s urban core was a bust.

Sockeye returns to the Kenai River – the state’s most popular sport fishery and a longtime battleground where sport and commercial fishermen constantly war over who should be allowed to catch the fish – came in near the projection, but it was set at about 1.4 million sockeye – or 38 percent – below the 20-year average of 2.26 million. 

And there were a lot of fishermen questioning the accuracy of the in-river sonar count given an unexpected onslaught of pinks in the Kenai and other streams and rivers draining into Cook Inlet.

Fish and Game biologists calculated that 1.4 million pinks – three times the biggest previous run – swarmed into the Kenai, but said they were generally confident of their sonar count of 1.85 million sockeye.

The sockeye count was itself 600,000 fish above the upper, in-river goal of 1.2 million because the fishing was so poor early in the season that most commercial fishermen gave up on the fishery.

The commercial catch of fewer than 700,000 sockeye for the season could only be considered a disaster.  The catch was even smaller than the 2018 harvest that led then-Gov. Bill Walker to declare an official disaster. 

Making sense of all of this is not really possible, admitted Rich Brenner, the state biologist in charge of salmon forecasts.

“We need more data,” he said.

Shooting in the dark

Aside from the Panhandle where the National Oceanic and Atmospheric Administration’s (NOAA) “Southeast Alaska Coastal Monitoring Project” samples the seaward migration of juvenile salmon, biologists have limited information as to what happens once 49th state salmon hit the spawning grounds.

They know how many fish enter key rivers. How successful they are in spawning they can generally calculate in longer-lived species from how many fish return after only a year in the ocean. That return provides some idea of what proportion of two-ocean and three-ocean fish will survive, but it is a crude yardstick.

For pinks – which are spawned late in summer one year, go to sea early the next year, and return the following year – biologists are largely forced to calculate returns on the basis of the trends of the averages in previous years.

And even where they know more, making sense of it is difficult. The NOAA surveys in Southeast found a shortage of out-migrating young salmon in 2019 that helped predict the dismal showing of adult fish in that part of the state this year, but nobody really knows why the production of young fish was so low.

A Southeast drought reducing the in-gravel flow of the water in the region’s smallish creeks and rivers could be one possibility either because spawning beds dried out and young fish suffocated or because eggs or alevins froze to death after cold winter temperatures drove ice deeper into stream beds with slow-moving water.

But nobody really knows, and once the fish enter the ocean – a nightmarish ecosystem of predator and prey where the only rule is that the big eat the little – interactions become really tangled. For instance, adult Pacific herring, a favored food of many salmon, feed on smaller fishes including young salmon, and even adult salmon are known to eat juvenile salmon. 

Throw in dozens of other species of fish acting in much the same way, and the food web becomes a four-dimensional maze best viewed from a distance, which poses a fundamental question:

Are the big oscillations of the 2010s – with commercial harvests averaging 230 million salmon in odd years while falling to an average of 124 million in even years – some sort of new norm?

“That’s a good question,” Brenner said. But he didn’t even want to hazard a guess at an answer.

“There are just too many variables,” he said, and yet there is that old pattern that has only become more pronounced in the new millennium.

CORRECTION: An early version of this story inflated the forecast sockeye return to the Kenai River by mistakenly using the number of sockeye forecast for all of Upper Cook Inlet.