Scientists: Warming ocean factor in collapse of cod fishery

For centuries, cod were the backbone of New England’s fisheries and a key species in the Gulf of Maine ecosystem. Even fishermen, who stayed well within the quota, effectively were overfishing. He said climate variances in the Atlantic and Pacific oceans along with changes in the position of Gulf Stream and global climate change are pushing cod population to the “verge of collapse”. It could have caused mistrust between scientists, managers, and fishermen.

It explains why the cod population has declined to just 3% to 4% of sustainable levels despite a series of harvesting restrictions by fisheries managers in 2010.

According to the report, recovery of Gulf of Maine cod depends on sound fishery management and on knowing water temperature.

The cod fish quotas also underwent changes by the fisheries thanks to total ignorance about the warming temperatures. Pershing conducted the work with researchers from his institution and several others in the USA including NOAA’s Earth System Research Laboratory in Boulder, Colorado, and Stony Brook University in New York.

Still, he was pleased that the researchers who did this study say it looks like cod will be able to persist in the Gulf of Maine, despite the warming trend.

And commercial cod landings fell to 1,000 tonnes in the Gulf of Maine in 2013, sliding from a recent high of 6,000 in 2009, according to the US Department of Commerce.

Cod is a valuable fishing industry, even despite years of restrictions put in place to save the population. “We really have to wrestle with these changes and be realistic about what they mean”. The unusual thing is that while there have been more than enough catches, the cod numbers have taken a nosedive due to a warmer current of water that has overtaken the surrounding seas.

The Atlantic cod, a fish that came to symbolize bounty to America’s colonial settlers, is on the brink of disappearing, despite years of fishing limits aimed at rebuilding stocks. Warming was the best predictor, they reported: When summer temperatures went up, the number of fish reaching maturity went down. By not accounting for such an influential change, fisheries set quota ceilings that were too high and inadvertently endorsed severe overfishing.

“That warmth is implicated, in this latest study, for the dramatic decrease in Gulf of Maine cod populations, and it is likely also responsible for the northward retreat of cold water-loving sea life including the iconic Maine Lobsters”.

Last year, a United Nations report revealed how global warming was forcing many fish populations toward the polar regions as cod are now thriving in cooler waters in Canada, Norway and even Greenland. And this may spell trouble ahead as the food webs surrounding the cod fish are further affected in a negative way.

The key to saving the cod, researchers say, is for fishery managers to take such temperature changes into account.

More adaptable approaches to management of fisheries could help resolve the problem in the future, said Katherine Mills from the Gulf of Maine Research Institute.

The study shows the risk of not including water temperature in fisheries models, especially for stocks like Gulf of Maine cod at the edge of their range. Fishery managers should have been eyeing a smaller bank account, because the warming had significantly limited how big it could get.