New Bedford, MA, USA
New Bedford, by thriving on the Georges Bank fishery, helped make Massachusetts the dominant cod-producing state. Rising ocean temperatures are pushing cod populations into colder waters, creating uncertainty for the local fishing industry and coastal communities dependent on it. The southern portion of Georges Bank has already seen a drop in cod abundance. 1
New Bedford, MA, is a historic fishing community that has thrived on the bounty of Georges Bank on the outer continental shelf. However, increasing water temperatures may make the storied fishing grounds of Georges Bank unfavorable for cod.2,7,8
Cod fishing is such an important part of New England's heritage and prosperity that a carving known as "the Sacred Cod" hangs in the Massachusetts State House.2 New Bedford, MA—where Herman Melville wrote Moby-Dick—is a historic community that has thrived on the cod fishery.
However, the dramatic decline of groundfish (cod, haddock, and flounder) stocks on Georges Bank has undermined the traditional economy of fishing communities such as New Bedford.2 Massachusetts remains the dominant cod-producing state, with landings in 2004 totaling 10.5 million pounds—valued at nearly $16 million.2 But rising ocean temperatures now threaten what remains of Georges Bank cod, compounding the pressures of overfishing, increasing coastal development, and pollution.2
Since 1950, global mean sea surface temperatures have risen roughly 1°F (0.6°C).3 In the Northeast, regional sea surface temperatures have already increased almost 2°F (1°C) since 1970.2 Increases in sea surface temperatures across the North Atlantic Basin have already triggered changes in the composition and biodiversity of zooplankton species.4 These changes have an impact on the regional ocean ecosystem, and the local fisheries that depend on them.5
Over the past century, cod landings in the Gulf of Maine and on Georges Bank have undergone large-scale fluctuations, and periods of low landings have corresponded with periods of high water temperatures (along with other factors).6 A comparison of the distribution and abundance of cod in the region during the relatively cold period from 1965 to 1969 and the warm period from 2000 to 2004 indicates that cod were more widely distributed in the colder period.2 Around the time of a 2007 study, Georges Bank was again experiencing low landing levels.6
What the Future Holds
Scientists expect global warming to continue altering the distribution and abundance of cod in northeastern waters.2 Many stages in the cod life cycle—from spawning and feeding behavior in adults to the growth and survival of young cod—are affected by temperature.2 According to studies, mean annual water temperatures higher than 47°F (8.5°C) are likely to lead to a decline in growth and survival to a harvestable size.2,7,8 Future sea surface temperature increases further affects cod distribution and abundance.6
Waters around Georges Bank are expected to approach the maximum temperature threshold for cod (a mean annual bottom temperature of 53.6°F or 12°C) during this century, if we do nothing to reduce carbon emissions.2,7,9
If, on the other hand, we take significant steps to curb emissions, Georges Bank could remain suitable for adult cod. However, these waters are already at the 47°F (8.3°C) threshold for cod recruitment, so productivity can be expected to decline as temperatures increase.2
Many other factors may affect the ecosystem and in turn affect cod abundance and distribution, including human activities such as overfishing, pollution, and coastal development.6 Global warming brings added uncertainty to the fishing industry—particularly if we do not act now to cut emissions—and the fate of the Northeast's cod industry hangs in the balance.