Science

Warming seas may scramble North America's fishing industry

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In a warmer world, boats targeting Atlantic cod, such as this one, might have to head farther north to find the fish.

Robert F. Bukaty/AP Photo

Get ready, seafood lovers: Climate change may complicate efforts to net your catch of the day. That’s because warming seas will force many of North America’s most valuable fish and shellfish stocks north in coming decades, a major new modeling study finds, potentially creating headaches for the fishing industry and government regulators. Some species could see their ranges shrink by half, whereas others are poised to expand into vast new territories more than 1000 kilometers north of their current homes.

“Basically, climate change is forcing species to move, jumbling up ecosystems,” says ecologist Malin Pinsky of Rutgers University in New Brunswick, New Jersey, who led the study with postdoctoral researcher James Morley, now at the University of North Carolina in Chapel Hill. “That’s not necessarily bad news. But we’ve already seen that even much smaller shifts in the distribution of marine species can cause real economic disruption, political friction, and challenges to fisheries managers. And here we are talking about potentially big shifts.”

Researchers have already shown that on land and in the sea, plants and animals are shifting their ranges in response to rising global temperatures. Trees that thrive in warmer climates, for example, are spreading into areas where frigid winters once made survival impossible. And species that need cooler weather are retreating from areas that have become too warm.

For the fishing industry, such shifts are beginning to have practical consequences. In some cases, boats must travel farther to fishing grounds, driving up costs. Processing facilities have had to move, causing job losses in some communities. Valuable stocks have also shifted to waters controlled by other countries, sparking conflicts over who has the right to lucrative catches.

To get a sense of how such range shifts might play out along North America’s coasts, Malin, Morley, and colleagues tapped a vast trove of data from research trawlers that made more than 136,000 trips in U.S. and Canadian waters between 1970 and 2015. Those and other data, including water temperature, depth, and seafloor composition, helped them identify the preferred habitats of 686 marine species. The researchers then used 16 climate models to assemble two scenarios for each species: one in which global temperatures rise more than 4°C by 2090; the other in which they rise by just 2°C.

Species shift northward under both scenarios, but the shifts were greater with the 4°C rise. Along the Atlantic coast, for instance, the center of many species’ ranges shifted some 600 kilometers north, with tropical species moving into previously temperate waters and northern species abandoning the southern parts of their ranges. On the Pacific coast, some species shifted north by more than 1500 kilometers.

The modeling also suggests warming will lead to bigger overall ranges for some species. In the northern Pacific, for example, the preferred habitat of two commercial species, jack mackerel and canary rockfish, could nearly double in size. But there are losers, too. Around Florida, the preferred habitat of a fish called the sheepshead drops by nearly half. The ranges of two especially lucrative fish, Alaska pollock and Atlantic cod, also could shrink.

Pinsky’s team is careful to note that such projections are still rough, and that researchers will need to learn more about how specific species behave and reproduce to forecast how they will respond to warming seas.

“We need a deeper understanding of the ecological interactions … to fully assess the likelihood of these predictions becoming reality,” agrees ecologist William Sydeman, president and senior scientist at the Farallon Institute for Advanced Ecosystem Research in Petaluma, California. But, he says the study, which he calls “impressive” and the “most comprehensive analysis attempted to date,” is still a useful starting point for thinking about how climate change might affect bringing that cod filet or clam fritter to your plate.

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