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Alaska’s shrinking salmon

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Still plenty of fish, but they’re getting smaller and smaller and smaller/Doug O’Harra photo

The season of the salmon in the waters surrounding Alaska’s urban core has opened with a warning that all might not be well in the North Pacific Ocean.

Once again, as was the case last year, returning fish appear to be shrunken in size. The average weight of a sockeye caught this week in the Copper River commercial fishery  150 miles southeast of Anchorage was 4.4 pounds. That’s more than 25 percent smaller than the long-term, 6-pound average for the catch.

No one at the Alaska Department of Fish and Game is, at this point, willing to stick his or her neck out to predict this is a harbinger of things to come, but that is clearly the worry.

“It’s certainly on our radar when (small size) was so widespread last year,” said Jack Erickson, fisheries research coordinator for the state’s Division of Commercial Fisheries.

Humpie-size sockeye were all too common in the 49th state in 2015. Bristol Bay salmon averaged “5.12 pounds, smaller than the historical average and the 2014 average of 5.92 pounds,” the Alaska Journal of Commerce reported.

Kodiak sockeye came in at a paltry 4.7 pounds. Copper River fish were just over 5 pounds, about a pound underweight but good compared to the start of this year. Southeast sockeye averaged 4.36 pounds, only about a half-pound heavier than the region’s pinks, according to Alaska Department of Fish and Game data.

The consensus among scientists at the time appeared to be that warm ocean waters associated with a strong El Nino event and what has been called simply “the blob” reduced the volume of forage fish in the North Pacific and/or attracted more competition.

“Warm ocean temperatures favor some species but not others,” the National Oceanic and Atmospheric Administration noted on its website in the fall of 2014. “For instance, sardines and albacore tuna often thrive in warmer conditions. Pacific Coast salmon and steelhead rely on cold-water nutrients, which they may have found recently in the narrow margin of cold water along the Northwest coast. But if the warmth continues or expands Pacific Northwest salmon and steelhead could suffer in coming years.

“‘If the warming persists for the whole summer and fall, some of the critters that do well in a colder, more productive ocean could suffer reduced growth, poor reproductive success and population declines,’ (ecologist Nate) Mantua said. ‘This has happened to marine mammals, sea birds and Pacific salmon in the past. At the same time, species that do well in warmer conditions may experience increased growth, survival and abundance.”

The warming  not only persisted through 2015, it continues to persist.

Before this year’s fishing began, Steve Moffitt, the state’s commercial fisheries biologist in Cordova, a fishing port near the mouth of the Copper River, was warning salmon might once again come back small.

“This wasn’t something that was unanticipated,” he said Friday. “My hypothesis is that they will be” smaller all year.

Hypothesis is the scientific word for an educated guess made before the data is available to provide an answer. Moffitt isn’t alone with this warm-water-drive hypothesis.

“They are small sockeye,” Erickson said. “We’ll see if this pattern holds.”

Less time spent at sea

Something clearly seems to be going on in the ocean, said regional sport fish research supervisor Jim Hasbrouck, because not only are sockeye smaller, Chinook – Alaska’s famous big kings – appear to be “maturing at a younger age.”

The latter change has been glaringly apparent on the fabled Kenai River where the big fish that made the river famous just aren’t there anymore. The reason, scientists agree, is pretty simple: Salmon that used to spend three, four or five years in the ocean are now coming back after a year or two

It’s almost as if the fish can sense that the data says there is no value in staying at sea longer. Three-ocean sockeye studied in Bristol Bay last year showed almost no growth after their second year in the ocean, Erickson said.

The age-structure of the sockeye return did not seem to have shifted as radically as it has for Kenai kings, however. Fish and Game still saw a good mix of age classes, Erickson said, but “the fish were smaller across all of them.

“They were smaller fish in all age classes.”

He is trying to remain optimistic that early returns to the Copper are just an anomaly, that as the season progresses the salmon will start coming back at something closer to normal average size. But – if NOAA’s warm water theory is correct – the odds on that aren’t good.

Not much seems to have changed offshore since 2015.

Just days ago the Alaska “Blob” Tracker was reporting “the blob lives.” Another post on the website warned that given the high water temperatures of the moment “we might be in for another  year of unusual species sightings in the Gulf of Alaska.” The “unusual species” would be warm-water fish showing up again off the 49th state.

Moffitt is hoping a forecast La Nina for the Pacific in the fall could shift things back toward normal, but worries that not even the upwelling of cooler water from deep in the ocean is no guarantee of change given the spread of warmth across hundreds of miles of the Gulf of Alaska.

And as of the moment, La Nina is more promise than reality.

“As the weeks pass, the layer of warm water at the surface contracts to the central Pacific and becomes very shallow, a sign that the current El Niño is on its way out,” writes Rebecca Lindsey at climate.gov. “By the final frame of the animation (model), the cold pool is just breaching the surface of the eastern Pacific off South America.”

The belief is a lot of that colder water will rise to the surface of the ocean and the North Pacific Gyre will start moving it north to mix with the Alaska Current, which should then start trying to finally kill the blob and return the Gulf of Alaska to something nearer normal.

At least in theory.

 

 

 

 

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1 reply »

  1. Perhaps the common murre, and their recent mass die-off in Southcentral, Alaska, has shown us what the problem is with salmon being smaller. Warming water drove the murres’ food source deeper than they could dive. At least that’s one theory. Could be the same with salmon. They are genetically programmed to live in a certain depth range in the ocean. If warm water drives much of their food source deeper than that range, the fish eat less and end up smaller.

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