October 29, 2015 — The rapid warming of the waters off New England has contributed to the historic collapse of the region’s cod population and has hampered its ability to rebound, according to a study that for the first time links climate change to the iconic species’ plummeting numbers.
Between 2004 and 2013, the mean surface temperature of the Gulf of Maine — extending from Cape Cod to Cape Sable in Nova Scotia — rose a remarkable 4 degrees, which the researchers attributed to shifts in the ocean currents caused by global warming.
The study, which was released Thursday by the journal Science, offers the latest evidence of climate change — this time, affecting a species once so plentiful that fishermen used to joke that they could walk across the Atlantic on the backs of cod.
Fisheries management officials have sharply limited cod fishing in hopes of protecting the species, but they estimate the number of cod remain at as little as 3 percent of what would sustain a healthy population. The limits, in turn, have hurt fishermen.
“Managers [of the fishery] kept reducing quotas, but the cod population kept declining,” said Andrew Pershing, the study’s lead author and chief scientific officer of the Gulf of Maine Research Institute in Portland. “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.”
The institute had reported last year that the rise in temperatures in the Gulf of Maine exceeded those found in 99 percent of the world’s other large bodies of saltwater. The authors of Thursday’s study link the rapid warming to a northward shift in the Gulf Stream and changes to other major currents in the Atlantic and Pacific oceans.
They say the warmer water coursing into the Gulf of Maine has reduced the number of new cod and led to fewer fish surviving into adulthood. Cod prefer cold water, which is why they have thrived for centuries off New England.
The precise causes for the reduced spawning are unclear, the researchers said, but they’re likely to include a decline in the availability of food for young cod, increased stress, and more hospitable conditions for predators. Cod larvae are View Story eaten by many species, including dogfish and herring; larger cod are preyed upon by seals, whose numbers have increased markedly in the region.
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