Claim:New England cod collapse linked to warming waters

Rapid warming in the Gulf of Maine helps explain why New England’s cod stocks are on the verge of collapse despite cuts to fishery activity, reports a new study. The results reveal how a warming climate complicates fisheries management. For centuries, Atlantic cod were pillars of New England’s fisheries, carefully managed by programs designed to reduce harvesting levels in response to low stock biomass. In 2010, when cod stocks were already low, fisheries managers placed a series of restrictions on harvesting this species, but even strict quota limits on fishermen failed to help cod rebound. To understand if ocean warming was contributing, Andrew Pershing et al. used sea surface temperature data dating back to 1982 to study temperature trends in the Gulf of Maine. Comparing changes in this region with global trends, they found that the ocean in the Gulf of Maine has warmed very rapidly; indeed, 99% faster than anywhere else on the planet between 2004 and 2013 – in part due to changes in the position of the Gulf Stream. The rapid warming reduced the number of new cod produced by spawning females, the researchers say, and led to fewer young fish surviving to adulthood. Because models used to set the quotas for cod over the last decade did not always account for the impact of rising temperatures, the number of new fish available was often overestimated, and resulting quotas were too high; even though fishermen stayed within them, more fish than the population could sustain were taken, Pershing et al. say. Their study highlights the importance of incorporating recent temperature data in models used by fisheries programs. Following analyses with a model used to project the rebuilding potential of the cod stock under future temperature scenarios, the researchers say how quickly this fishery rebuilds now depends on both sound management and favorable temperatures.

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