Warming waters are destroying the New England cod population

OCTOBER 30, 2015

by Eric Hopton

   

Supplies of cod, once the lifeblood of the New England fishery and a key species in the local ecosystem, have collapsed. Despite the best efforts of fishermen and fishery managers, attempts to reverse the devastating decline were too little and too late and the Gulf of Maine cod industry is done for.

Cod populations have failed to adapt to the ocean warming, and today stock levels are only 3 to 4 percent of what is needed for a sustainable fishery. Even when cuts to the numbers of fish landed and strict quota limits were introduced in 2010, the decline accelerated, leaving both fishermen and fisheries managers puzzled and disappointed.

Now, a new report in the journal Science offers an explanation. The steady pace of warming caused by global climate change was exacerbated by changes in the position of the Gulf Stream and by climate oscillations in the Atlantic and the Pacific oceans. With this triple assault on local water temperatures, no amount of stock management was going to help.

“Managers kept reducing quotas, but the cod population kept declining,” said Andrew Pershing, Chief Scientific Officer of the Gulf of Maine Research Institute (GMRI). Pershing was the lead author of the study and added: “It turns out that warming waters were making the Gulf of Maine less hospitable for cod, and the management response was too slow to keep up with the changes.”

Waters too hot for cold water cod

The researchers found the root of the problem was that increasing water temperatures reduced the number of new cod produced by spawning females, and it also led to fewer young fish surviving to adulthood.

Previous models used by fishery managers over the last decade to set quotas did not take into account the impact of rising temperatures. As a result, even though fishermen stuck to the big reductions in quotas, they were still unknowingly taking more fish than the population could sustain.

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