As sea ice melts, fish are showing up farther north off Alaska. A federal fishing trip will investigate if they’re sticking around.

Last fall, Adem Boeckmann, a commercial fisherman who lives outside Nome, pulled up some of the pots he uses to fish for crab on the ocean floor.

“Had 10 24-inch cod in each pot,” Boeckmann said. “I never saw anything like that.”

Cod, which is used in fish sticks and fish and chips, is caught in huge numbers by commercial boats in the Bering Sea. But not near Nome – typically, the fish is caught hundreds of miles south. Historically, the ecosystem where Boeckmann fishes has been centered on the ocean floor, without big populations of large fish.

Adem Boeckmann. (Courtesy of Adem Boeckmann)

Federal scientists are setting off on their own Bering Sea fishing trip this summer, to investigate whether observations like Boeckmann’s – bolstered by the government’s own previous findings – could be indicators of profound shifts in the ocean ecosystem driven by global warming. The results of the summer fieldwork could have major implications for the Bering Sea’s billion-dollar fisheries, as well as for Alaskans who live, hunt and fish along the Arctic coast.

“Is this part of an environmental shift, where with the warming, the northern Bering Sea is going to become a top-down system?” asked Lyle Britt, a federal fisheries scientist who will spend more than a month at sea this summer. “Or, is this more like an ephemeral trend that just happened because we had an unusually warm year, and things will reset? We don’t really know.”

The surveys are done by the Seattle-based Alaska Fisheries Science Center, an arm of the National Oceanic and Atmospheric Administration.

This year’s effort should provide especially useful data, scientists say, because it will include the northern part of the Bering Sea. Researchers have been surveying the Eastern Bering Sea for decades, and it is also included in this summer’s work.

But full surveys of the Northern Bering Sea have been far less frequent, with the two most recent in 2010 and 2017. Scientists will return there this summer, and they’re hoping to collect new data to help them explain the dramatic differences between the two previous northern surveys.

These two photos show federal scientists’ catch at the same Bering Sea survey station in 2018 (left) and 2010. The 2010 catch was primarily a small fish called capelin, while the 2018 survey caught much-larger pollock. (Courtesy NOAA Fisheries)

In 2010, the results showed that pollock was absent from the Northern Bering Sea in large numbers – the estimated biomass was just 20,000 tons, with cod biomass estimated at 29,000 tons. In 2017 – a warmer year with lower sea ice – the survey results showed 1.3 million tons of pollock, and another 280,000 tons of cod.

Federal scientists will start three months of surveys Friday from the port of Dutch Harbor, in the Aleutian Islands. They’ll work 13-hour days from hired fishing boats, dividing the Bering Sea into a grid of hundreds of 20-mile squares.

At each square, they’ll drop a 50-foot-wide trawl net into the water, drag it just above the ocean floor for a couple of miles, then pull it back out. Then, they’ll dump the contents on to a table to be sorted, to help scientists see what’s in the water.

“It is all very much alive and moving around,” Britt said. “If we tow in a spot where we get a lot of, say, king crab, you’ll watch this big pile of what looks like red spiders heading off across the deck, and you’ve got to go get them.”

This year’s survey should give scientists more insight into whether the results from 2017 – the ones that showed huge amounts of pollock and cod in the northern Bering Sea – reflected an isolated event or the start of a long-term trend. Ice cover in the Bering Sea was close to normal in the early part of this past winter and only declined to abnormal levels after January, according to NOAA.

Pollock, seen here at a processing plant in Dutch Harbor, in the Aleutian Islands, are one of the species being found in increasing numbers in the northern Bering Sea. (Photo by Berett Wilber)

Commercial fishing groups are among the stakeholders closely watching this summer’s surveys, since the results could have ramifications for the eastern Bering Sea cod and pollock fisheries, worth an estimated $2 billion. Captains have already seen a “gradual shift northward” in their cod fishing patterns, said Chad See, executive director of the Freezer Longline Coalition, an industry group.

But researchers and fishermen still want more information about where the northern Bering Sea cod came from. Did they swim there from fishing grounds in the Eastern Bering Sea? Or did they come from elsewhere, like Russian waters to the west? If they swam north from eastern Bering Sea, that would help explain why scientists didn’t find more cod in the fishing grounds in their 2017 survey, See said.

“If it’s the same stock, one might say that the health of the stock, at least from a biomass perspective, is still very strong,” See said. “If the fish in the eastern Bering Sea just disappeared, we have a different problem entirely.”

Residents of the towns and villages along the Bering Sea are paying attention, too. Warming temperatures and diminished sea ice could have major impacts on the marine mammals that people target in subsistence hunts, and on the smaller organisms that those marine mammals eat, said Wes Jones, director of fisheries research and development at Norton Sound Economic Development Corp.

NSEDC uses profits from its shares of federal commercial fishing quotas to pay for economic development programs in the Bering Strait region, which extends from Unalakleet to Nome to more remote coastal villages, like Wales.

Residents have been seeing shifts in the Bering Sea ecosystem for decades, said Laureli Ivanoff, an NSEDC spokeswoman.

Adem Kougarok Boeckmann and Anvil Kain Boeckmann stand above crab they caught from Norton Sound on the boat run by their father, Adem Boeckmann. (Courtesy Adem Boeckmann)

“Our communities and the people who have seen the changes are relieved Western science is now paying attention,” Ivanoff said.

Residents have been pushing for more involvement with federal scientific work in the region, and one of NSEDC’s biologists will participate in this summer’s northern Bering Sea survey, Jones added.

Meanwhile, small-boat fishermen in the region, like Boeckmann, are looking to the survey’s results to help them make decisions about how to respond to possible shifts in crab and fish stocks. Boeckmann has contemplated spending $30,000 on new gear that would allow him to commercially fish for cod.

But before he does that, Boeckmann said, he wants to know he’ll be able to consistently earn a profit. He recounted a conversation with a federal scientist who suggested that as quickly as the cod showed up off Nome, they could also disappear.

“Things have changed, absolutely,” Boeckmann said. “But there’s nothing saying it’s not going to flop right back to what it was for 100-plus years, tomorrow.”

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