The effects of climate change are being felt in regional fisheries, causing a scientist at the Woods Hole Oceanographic Institution to predict that haddock will disappear from the North Atlantic within 70 years. A 3-D underwater camera helped confirm the numbers.
Results from the Global Ocean Ecosystem Dynamics (GLOBEC) program indicate that Arctic ice melt has made its way to the Gulf of Maine and Georges Bank, said Cabell S. Davis, a WHOI senior biologist.
The influx of fresh water has lowered the natural salinity of these productive fishing grounds—and coupled with rising water temperature, the impacts will be felt across the entire ecosystem, he said.
Towing an underwater video camera from the Azores to Woods Hole, Dr. Davis captured thousands of images of copepods, a food source for cod and haddock larvae, and even right whales. Putting a computer model to work, the GLOBEC team found that decreased salinity led to an earlier spring bloom of phytoplankton, the main food source for copepods.
The result was a three-fold increase in copepod populations on Georges Bank from 1995 to 1999. Longer term data sets revealed that the water in the 1990s was more fresh and had more copepods than the 1980s.
Pointing to the 2003 haddock harvest, the best year for that fishery since 1963, Dr. Davis said the changes can initially be a good thing for fish. An earlier spring bloom of phytoplankton means that copecods have more food. Higher concentrations of copepods will allow the infant cod and haddock to grow faster, and thus have better survival rates.
However, not all copecods are created equal, Dr. Davis said. There are two types living in the western North Atlantic: one cold-water species, and one tropical species. The warm-water copepod, Centropages typicus, swims too fast for the larval fish to catch.
Already, Dr. Davis said, these copepod populations have doubled in the Mid-Atlantic Bight, off New York and New Jersey, since 1977.
“Potentially, cod and haddock larvae won’t have anything to eat,” said Dr. Davis, speaking at a Marine Biological Laboratory Ecosystems Center seminar last week.
“Even with best management practices, if the projected warming trend happens in the Gulf of Maine and Georges Bank, cod and haddock could be gone by 2080.”
Worst-case scenarios
Dr. Davis based his models on a medium prediction of climate change, established by an International Panel on Climate Change scenario that includes a mix of fossil fuel and renewable energy to drive the economy. If Artic melting occurs more rapidly than the predictions—which has already been the case—Dr. Davis said that the effects on fisheries could be worse.
“As more melting occurs, the nutrients on the surface sink, leading to a decrease in productivity. In addition, a climate pattern, called the North Atlantic Oscillation, affects how deep Labrador Sea water flows southward to New York, bringing in colder, low salinity water with lower nutrients,” Dr. Davis said.
Further research will be needed to study the consequences of this ecosystem shift, and other effects of climate change, on other commercially important species, including adult cod, haddock, scallops, and lobsters.
Tags: Cabell Davis, Climate Change, commercial fisheries, copepods, Georges Bank, global warming, GLOBEC, phytoplankton, salinity, underwater video, Woods Hole Oceanographic Institution
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