Management not keeping up with changing conditions
The Gulf of Maine is simply getting too warm for cod, fisheries experts said in a new study released this week that links the warming to changes in the position of the Gulf Stream and to climate oscillations in the Atlantic and the Pacific. These factors add to the steady pace of warming caused by global climate change.
Cod stocks, once the mainstay of New England’s fisheries, are on the brink of collapse, hovering at 3 to 4 percent of sustainable levels. Even strict quota limits on fishermen failed to help cod rebound, and that’s unlikely to change any time soon, the researchers reported in the journal Science.“Managers kept reducing quotas, but the cod population kept declining,” said Andrew Pershing, chief scientific officer of the Gulf of Maine Research Institute and lead author of the study. “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.”
After studying population trends, Pershing and fellow researchers concluded that the warmer water reduce the number of new cod produced by spawning females. Their study also suggests that warming waters led to fewer young fish surviving to adulthood.
The models used by managers over the last decade to set the quotas for cod did not account for the impact of rising temperatures, leading to quotas that were too high. Fishermen stayed within their quotas, but still took more fish than the population could sustain.
“This creates a frustrating situation that contributes to mistrust between fishermen, scientists, and managers,” Pershing said. “The first step toward adapting fisheries to a changing climate is recognizing that warming impacts fish populations.”
According to the report, recovery of Gulf of Maine cod depends on sound fishery management and on future temperatures. Cod are a coldwater species, and the Gulf of Maine is at the edge of their geographic range. As the ocean warms, the capacity of the Gulf of Maine to support cod will decline, leading to a smaller population and a smaller fishery.
The study shows the risk of not including temperature in fisheries models, especially for stocks like Gulf of Maine cod that are at the edge of their range. The warmer our climate gets, the less fisheries managers can rely on historical data.