Zach Whitener, research associate at the Gulf of Maine Research Institute, holds a cod while collecting samples for a study. PHOTO: Gulf of Maine Research Institute

As climate change has warmed the Earth, oceans have responded more slowly than land environments. But scientific research is finding that marine ecosystems can be far more sensitive to even the most modest temperature change. A telling effect of rising temperatures is the problems fishing is plagued by.

Cod was once so plentiful in New England that legend had it you could walk across the local waters by stepping on the backs of the fish. Now, though, this tasty species is in such trouble there that cod fishing is practically shut down. And scientists say it looks like rapid warming in the Gulf of Maine explains why regulators’ recent efforts to help the cod while allowing fishing were a failure.

“Year after year, as they looked at the population, they realized that there were fewer cod than they expected there to be,” says Andrew Pershing, an oceanographer at the Gulf of Maine Research Institute. “They thought that they should be rebuilding, but they were actually declining.”

At the same time the cod were mysteriously failing to rebound, he says, strange things were happening on the shores of Maine. People were finding seahorses, which almost never go that far north.

“We had squid we don’t normally find here,” recalls Pershing, “we had species like black sea bass that are normally found around Long Island that were hanging out in the lobster traps here in Maine.”

These oddities were happening because the Gulf of Maine was warming. In the journal Science, Pershing and his colleagues say the warming was also hurting the cod — and managers didn’t take it into account when setting their fishing quotas. That means even if people didn’t exceed their quotas, too much cod got taken.

“In really warm years, every female cod produces fewer babies than we would expect, and we also see that the young fish are less likely to survive and become adults,” says Pershing.

Ecosystems all around the world are warming up due to global climate change, says Pershing, but the Gulf of Maine is ahead of the curve. Over the last decade, it’s warmed faster than 99.9 percent of the global ocean.

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