Pacific cod (Photo Courtesy of Holland Dotts & the Alaska Marine Conservation Council)

In an unprecedented response to historically low numbers of Pacific cod, the federal cod fishery in the Gulf of Alaska is closing for the 2020 season. It’s a decision that came as little surprise, but it’s the first time the fishery has closed due to concerns of low stock.

“We’re on the knife’s edge of this over-fished status,” North Pacific Fisheries Management Council member Nicole Kimball said during talks in Anchorage Friday afternoon.

It’s not over-fishing to blame for the die-off, but rather, climate change.

Warming ocean temperatures linked to climate change are wreaking havoc on a number of Alaska’s fisheries, worrying biologists, locals and fishermen with low returns that jeopardize fishing livelihoods.

A stock assessment this fall put Gulf cod populations at a historic low, with “next to no” new eggs, according to NOAA research biologist Steve Barbeaux, who authored the report.

At their current numbers, cod are below the federal threshold that protects them as a food source for endangered Steller sea lions. Once below that line, the total allowable catch goes to zero — in other words, the fishery shuts down.

Related: Battered by a marine heat wave, Kodiak’s cod fishermen may not be fishing in the gulf for much longer

After the report was released, the stock assessment still had to pass through the NPFMC for review. The council unanimously passed the final decision to close the fishery Friday in Anchorage.

Up until the emergence of a marine heatwave known as “the blob” in 2014, Gulf cod was doing well. But the heat wave caused ocean temperatures to rise 4-5 degrees. Young cod started dying off, scientists said.

“A lot of the impact on the population was due to that first heat wave that we haven’t recovered from,” Barbeaux said during an interview last month. Following the first heat wave, cod numbers crashed by more than half, from 113,830 metric tons in 2014 to 46,080 metric tons in 2017.

The decline was steady from there.

“Retrospectively, we probably should have shut the fishery down last year [too],” Barbeaux said.

Cod only enter the fishery at age three, so the environmental effects on the fishery are somewhat delayed. There are now signs of a second warming event. Scientists like Barbeaux and say it’s hard to predict what the future of the fishery will look like.

“We’re just well beyond what we’ve ever seen before. It’s this very unusual, warm event,” said Mike Litzow, a NOAA fisheries ecologist based in Kodiak. “What the climate scientists are showing us, our best understanding is that this is going to be the new average within a short time frame.”

Related: There’s a new fight over Bering Sea black cod. Warming water may be to blame.

With uncertainty looming, Gulf cod fishermen in Kodiak are struggling with a decline of what used to be a major part of the island’s winter economy. Many fishermen have already moved on from cod. For the few remaining, the federal fishery closure further jeopardizes their livelihoods. State cod fishery limits for 2020 have yet to be set.

“It’s kind of devastating,” Kodiak-based pot cod fisherman Frank Miles said last month, hoping at the time that the situation would turn around for next year’s season.

Before the first heat wave, Miles said about 70 percent of his income came from cod fishing. Since then he’s worked to diversify, but he’s still concerned for the future.

Related: Amid a big fight for cod in the Bering Sea, can remote Adak survive?

“I’m more worried about my son and his generation, the younger guys coming up,” he said. “I’m 60, I’m probably just about done. I’d like to think that I could fish cod one more time before I retire, but I don’t know. I simply don’t know where we’re going here.”