Global warming will drive many of North America's fish species hundreds of miles northward, potentially costing coastal fishing communities billions of dollars over the next few decades, new research shows.

In New England, the centuries-old cod fishery is at risk, with East Coast habitat for Atlantic cod expected to decline 90 percent by 2100. Off the Pacific Northwest, rockfish that have been prized by Native American communities for centuries are moving toward Alaska as the oceans warm.

If heat-trapping greenhouse gas emissions continue unchecked, several important species will disappear from their current habitat by the end of the century, according to a new study of 686 species that live in the relatively shallow waters along the North American continental shelf. The biggest changes are expected along the West Coast, where some economically important species like rockfish will move some 900 miles from their traditional grounds off Washington and Canada to Alaska.

Even if global warming is limited to no more than 2 degrees Celsius, as intended under the Paris climate agreement, there will still be increasing disruptions to fisheries. The shifts have already caused conflicts over the regional fishing quotas, said Rutgers University researcher Malin Pinsky, co-author of the new study published this week in the journal PLOS One.

Like other species, fish are trying to keep cool in the face of global warming, but since they are highly mobile, they are occupying new habitat 10 times faster than species on land, Pinsky said.

That's going to have an impact on humans, too.

Sign up for InsideClimate News Weekly Our stories. Your inbox. Every weekend.

"It's like the rug is slowly getting pulled out from under our fishing communities," Pinsky said. "This is something that's been playing out on the East Coast already. If we don't start to get ready for that, it's going to create more conflict and challenges for fishing communities in the future."

In the Gulf of Maine, for example, one of the fastest-warming ocean areas globally, the temperatures are predicted to become less suitable almost across the board for cod, flounder and pollock, three traditional mainstays of the fishing industry.

In a future with high greenhouse gas emissions, the waters in that region would warm by another 2 to 4 degrees Celsius by 2100, pushing cod several hundred miles up the coast to Canada and possibly out of reach of fleets based in Bangor and Rockport.

A Big Financial Hit for the Industry

Globally, climate change could take a $10 billion bite out of fishing revenues by 2050, with developing countries suffering the most, according to Vicky Lam, a University of British Columbia fisheries scientist who co-authored a 2016 study quantifying the financial cost of climate change to fisheries.

In a high greenhouse gas emissions scenario (one resulting in an average global temperature increase of about 5 degrees Celsius by 2100), U.S. fishing revenues would decline 11 percent by 2050, the researchers found. If global warming is limited to about 1.5 degrees Celsius, the U.S. decline would be 8 percent, she said.

The temperature increases are expected to play out in different ways in different parts of oceans in a nuanced pattern influenced by currents, ocean depth and seafloor topography. In the key West Coast and Northeast fishing regions, water temperatures where fish live are projected to warm by 1 to 4 degrees Celsius by 2100.

Lam said the climate change impacts to fisheries would hit even harder in developing countries in Asia and Africa, where fish are the main daily source of food in many coastal communities, and where fishers have fewer resources to adapt. The loss would also have ripple effects, like fewer jobs in fish processing and handling. Fishing fleets and communities in developed countries could be stymied.

"It's not that easy to change target species, to change gear and fishing techniques, and the market might not be able to adapt," she said, explaining that there may be no demand for new and unfamiliar species.

Urgency and Equity

In the new study, the researchers used data from thousands of scientific fish surveys to show where the fish live now and how they've already moved in response to climate change.

Using global climate models, they projected how ocean temperatures will change along the North American coasts, and how fish populations will shift based on the temperature tolerance of various species.

"We have long-term historical records of where these fish are on the continental shelf, so we're able to make projections for a wide range of species. This study clarifies how far many of the important species will shift," Pinsky said.

It's a bigger shift than projected by earlier studies.

The scientists suspect that over the next few decades, the pace of change in the oceans will accelerate. That makes it even more urgent to figure out how fishing communities can transition.

In the worst-case scenario, some species could become much less abundant with few other species to take their place.

"That raises tough questions about fairness and equity," Pinsky said. Fish limits are one issue. For example, "along parts of the New England coast, summer flounder and black bass are becoming more abundant—people there want to fish them because other species have become less abundant." But the allocation and permitting isn't keeping up with the rapid pace of change, which makes adaptation harder.

"Accounting for climate change injects more certainty. If we pretend like nothing is happening, it's not going to help," he said.

Tribes Are Concerned on the West Coast

The findings are not welcome news for Tom Moore, an oceanographer with the Northwest Indian Fisheries Commission, a natural resources management support service organization for 20 Indian tribes in western Washington.

"A lot of the tribes are heavily invested in coastal fisheries. This will have a tremendous impact," Moore said. "These fisheries have had a very specific cultural meaning from time immemorial. All the tribes depend on fisheries."

The tribal fishing rights, fixed by treaty, are place-based, linked to historic fishing grounds from the pre-colonization era. That means the Native communities can't simply catch their allocation of fish somewhere else if the fish move.

"You'll have to adapt the fisheries and see what species are coming up from Southern California and Mexico. There are already tropical species moving north," he said.

Moore said the new study is an important step for future management of fish, with big financial implications.

"If you're making investment in a future fishery, buying new boats and gear, you want to make sure it's going to be there in 20, 30, 50 years," he said.

In the Gulf of Maine

The New England fishery is one of America's oldest industries, and helped build the country's early wealth, said Ben Martens, director of the Maine Coast Fishermen's Association.

Generations of fishermen have adapted to booms and busts in fish populations there. In the late 1800s, halibut populations crashed in one of the first signs of overfishing. But that was long before the recent, pronounced warming of oceans, which varies from one basin to another but has been carefully confirmed worldwide.

The U.S. seafood industry today supports more than $200 billion in economic activity and about 1.6 million jobs, according to the latest U.S. fisheries report from the National Oceanic and Atmospheric Administration (NOAA). The agency has warned in its national climate science strategy for fisheries and regional action plans that climate change impacts will ripple through coastal communities and seafood businesses.

"Warming waters is probably a piece of what's happening, but it's not the whole story," Martens said. "There are impacts up and down the food chain. We have big boats chasing herring, which the cod like to eat. I get really nervous when people say climate change is coming and we can't rebuild fish stocks. There are a lot of things we can do in the short term."

Not all the changes will be negative, said James Morley, lead author of the new study. The findings show ocean conditions will become more favorable for other species as temperature rise, including black sea bass, summer flounder and new species of squid. Some tropical species' ranges will expand, like gray snapper, which could be found throughout the Gulf of Mexico and the southeastern U.S. by 2100.

But making sure that fishers have access to new species requires a flexible and well-informed science-based management approach that can allocate catch quotas and set size restrictions to maintain sustainable stocks, he said.

"Even in areas where predictions are positive, there are still is going to be increasing conflicts. The fish have shifted, but the quotas haven't shifted along with that."

Morley said fisheries managers also have to track complex interactions among different species in the Gulf of Maine. As squid became more abundant, they started to eat more shrimp, reducing the catch of that species. Species of sea bass moving north are also likely prey on young lobsters, which could affect a critically important New England fishery in the long run, he said.

The future trajectory of greenhouse gas emissions is critical for projecting the changes.

"The amount of carbon emissions has a huge impact on the magnitude of these shifts. An extra couple of degrees of warming increases in the magnitude of shifts by a factor of three or four," he said.