LAKSHMI SINGH, HOST:
From balloons to the blob - that is causing problems in the waters off Alaska. The cod population in the Gulf of Alaska is at its lowest level on record.
From Alaska's Energy Desk, Annie Feidt reports the culprit is the blob, a warm water mass that churned in the ocean for more than three years.
ANNIE FEIDT, BYLINE: Darius Kasprzak has mostly given up on finding cod. But on a calm day, he takes me out on his boat to show me where he used to catch them by the hundreds.
DARIUS KASPRZAK: That might be something.
FEIDT: We're in a bay right near Kodiak, an island town that sits on the western edge of the Gulf of Alaska, some of the most productive fishing waters on earth.
Kasprzak looks at his echo sounder screen and sees a dense cluster of dots on the ocean bottom.
KASPRZAK: OK, let's drop on it. Just - oh, you know, that looks pretty darn good. Oh, that looks real good, actually.
FEIDT: He kills the engine, leaps onto the deck and lowers one of his fishing lines into the water. And then, nothing.
KASPRZAK: That's the weight coming up.
FEIDT: Kasprzak has gotten used to his fishing lines coming up empty.
Between 2013 and 2017, a warmer-than-normal mass of water called the blob occupied a huge swath of the Pacific. At its peak, it reached from Alaska to South America. In the Gulf of Alaska, the cod population plummeted by more than 80 percent. Climate change didn't cause the blob all on its own, but scientists say global warming made it worse.
Kasprzak says he used to think the rich ocean ecosystem he fishes was unshakable.
KASPRZAK: We've just seen now that even the mighty Gulf of Alaska - how fragile it actually is when all you've got to do is warm it up. Don't even warm it up that much - a couple of degrees. It doesn't take that much.
FEIDT: The temperature of the Gulf of Alaska has returned to close to normal. And now everyone in Kodiak is asking will the cod come back?
MIKE LITZOW: There's all kinds of information you can get sort of over time once you catch the fish.
FEIDT: Mike Litzow is a fisheries biologist with the University of Alaska. He's standing in shallow water near shore, pulling in a fishing net. He wants to catch young cod.
LITZOW: Scuplins, another greenling, another greenling.
FEIDT: No cod in this net. But by the end of the summer, Litzow hopes to catch enough tiny cod to provide clues on whether the population will recover.
Litzow says the blob is a kind of dress rehearsal for the future. As climate change warms oceans around the world, these marine heat waves are expected to happen more often. And he says it's really hard to predict what kind of ripple effects that will have.
LITZOW: If you had said to a bunch of biologists, OK, the Gulf of Alaska is 3 1/2 or 2 degrees warmer than normal for a whole year, it would just be like drawing names out of a hat, you know? It's not like all of the scientists would say cod are going to be the ones that collapse.
FEIDT: Litzow says when one species declines, others do well. Right now, sablefish are booming in the Gulf of Alaska.
But Litzow doubts cod will come back, and that could be a disaster for fishermen and the community of Kodiak. Already, cod boats are traveling more than a thousand miles away to find fish. That means the crews aren't stocking up at stores in town and the boats aren't paying the local fish tax.
KASPRZAK: Just had a nibble there, but I think he got off.
FEIDT: Back on his boat after four hours, Darius Kasprzak sees some puffins, even a whale, but no cod. Eventually, he gives up. Now he just wants a few fish for dinner, some dusky rockfish.
KASPRZAK: Yay, we got a dusky. We got dinner. Woohoo. That's a big one, too. Nice.
FEIDT: It's dinner, but it's not a living. He's considered trolling for salmon, but that would require an expensive new permit and gear. And many salmon runs have been weak, too.
KASPRZAK: All right, I think we can go home now.
FEIDT: Kasprzak is looking at other career options, but he says he wants to stay in Kodiak as long as he can. That way, if the cod do come back, he'll be one of the first ones out on the water.
For NPR News, I'm Annie Feidt in Kodiak, Alaska.
SINGH: That report comes from Alaska's Energy Desk, a public media collaboration focused on energy and the environment.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.