“Our management forecasts were failing because we were not accounting for this very rapid change in temperature”, said Andrew Thomas, an oceanographer at the University of Maine and a co-author of the study.
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Janet Nye is a Professor in the School of Marine and Atmospherics Sciences at Stony Brook University in New York.
These warming temperatures led to fewer offspring and fewer young fish surviving until adulthood. Now, there’s only three percent of what would constitute a healthy cod population left.
This new finding may not be welcome to fishermen, whose fishing practices have already been reduced due to previous restrictions.
At the center of the new study is a demonstration of just how tightly all of this is related to warm waters. The researchers think temperature is partly to blame. Thus, in effect, they say cod were overfished because ocean warming wasn’t adequately considered in fishing quotas.
The effect has not, to be sure, been the same for all species. Instead, he said, they should set quotas that reflect the status of the stock.
Not all Atlantic cod populations have fared poorly with warming water temperatures, though. These factors added to the steady pace of warming caused by global climate change. “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”. Researchers have seen spawning aggregations – kilometre-wide columns of adult cod reaching up to 150 metres off the seafloor – off northern Newfoundland and Labrador for the first time since 1992. “The Gulf of Maine, for cod, is really at the warm end of that”, Pershing said.
From 1982 to 2013, water temperature in the Gulf of Maine increased more than most other parts of the ocean – 0.03 degreesCelsius per year compared with a global average of 0.01 degrees per year.
For that reason, the key solution that the researchers advocate is better integration of climate modeling in decision about where, when, and how cod fishing should be allowed. Hilborn says that even with slightly warming waters, the Norwegian stock is at record levels now. By law in the U.S., you shouldn’t be in a position where that recovery process would take more than 10 years.
Scientists like Mann have also linked warm ocean temperatures off New England to the dramatic snowfalls that Boston experienced earlier this year – noting that warmer water means there is more moisture in the atmosphere above it. And this moisture, if swept up in a storm, can produce more precipitation.
Using recent Gulf of Maine cod stock assessments, the researchers then tested a number of models for predicting the factors that affected cod reproduction.
And research to understand the other consequences of such stark ocean warming in the Gulf of Maine and off of the coast of New England has only begun.
“We’re seeing an ecosystem going through a really massive change, and I really want my colleagues to look at this”.
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The research should serve as impetus for a long-needed overhaul in how fish are managed in the region, says biologist Jud Crawford of The Pew Charitable Trusts’ northeast oceans program in Boston, who was not involved in the study.
