The cod fishery off the Northeast coast of the United States has collapsed despite smarter fishing practices, because waters in the Gulf of Maine have warmed much faster than the rest of the ocean, a new study has found.
The study focuses solely on the region, and does not necessarily reflect the impact of warming waters on fisheries in other parts of the world. But what’s happening in the Gulf of Maine could be the beginning of a broader trend, some say, and the findings could push industry experts and policymakers who are shaping long-term conservation efforts to factor in the effects of temperature when estimating fishing quotas.
“The failure to consider temperature impacts on Gulf of Maine cod recruitment created unrealistic expectations for how large this stock can be and how quickly it can rebuild,” the researchers wrote in the study, published online Thursday in the journal Science. “Thus, how quickly this fishery rebuilds now depends arguably as much on temperature as it does on fishing.”
Global warming has for years caused temperatures to rise in oceans around the world. Between 2004 and 2013, however, the Gulf of Maine warmed at a rate of about 0.23 degrees C a year – faster than 99.9 percent of the world’s oceans, the researchers found.
One contributing factor in that warming is a northward shift in the Gulf Stream. “[S]ome of the warm water it carries is able to work its way into coastal waters, including the Gulf of Maine,” study coauthor Michael Alexander, a meteorologist at the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory, told the Bangor Daily News.
The resulting rapid change in temperature aggravated the already-declining populations of cod in the Northeast. In 2013, the region’s fishery management officials imposed drastic cuts in an effort to save the centuries-old industry, The New York Times reported at the time. But the effort fell short – partly because it failed to take into account the impact of rapidly warming waters.
Between 2001 and 2013, the catch of Atlantic cod fell from more than 33 million pounds to less than 5 million, The Associated Press reports.
The researchers were quick to point out that both the environment and humans have played a role in the population’s collapse.
“Let me be clear, if there were no fishing of cod, it would not have collapsed,” said Janet Nye, a coauthor of the study and assistant professor at the School of Marine and Atmospheric Sciences at Stony Brook University in New York, at a press briefing Thursday.
“Gulf of Maine cod would have most certainly responded to this unprecedented warming event and abundance would have declined,” she said. “But Gulf of Maine cod would not have collapsed without fishing. It was the combination of fishing and environmental variability that caused this iconic stock to finally collapse.”
Still, consumers aren't likely to feel the consequences of the collapse – for now.
“Most cod in the [US] is now imported from places like Iceland and Norway or is Pacific cod from Alaska,” Andrew Pershing, chief scientific officer of the Gulf of Maine Research Institute and lead author of the study, told Smithsonian.com. “These stocks are currently doing well.”
But, he added, “We suspect that there may be other species, in the Northeast and elsewhere, that are being impacted by warming waters in a similar way. We are seeing a remarkable change in this ecosystem, and we need to figure out the short- and long-term impacts on the species we care about.”
• Staff writer Pete Spotts contributed to this report.