‘Ripple effect’ as fish opt for cooler water?

"As temperatures have warmed in the waters off our coasts, animals with a low tolerance for that warming have just picked up and shifted," says Malin Pinsky. (Credit: Kevin Bryant/Flickr)

Increasing temperatures are pushing fish and crustaceans north in search of cooler waters along the east and west coasts of North America.

The shift could have an effect on birds, marine mammals, and those who depend on fishing for food and income.


For example, lobsters that were once abundant off Long Island have moved to cooler waters of Maine while summer flounder and black sea bass, once common to the waters off Cape Hatteras, have moved north and are now more abundant off the coast of New Jersey.

“As temperatures have warmed in the waters off our coasts, animals with a low tolerance for that warming have just picked up and shifted,” says Malin Pinsky, assistant professor of ecology and evolution at Rutgers.

“I hesitate to say ‘moved,’ mainly because we don’t yet know whether fish are actually swimming, or whether they’re simply reproducing more slowly in their old ranges and faster in their new ranges.”

Researchers say the shift northward is happening at different rates among species—not because of their biological differences—but because of the rate and direction of climate change in their waters.

During the past 18 months, Pinsky has published two papers—in Climatic Change in October 2012 and in Science in September 2013—documenting the trend and exploring its implications. The data is now available at a new website, OceanAdapt.

Much of the information on the website helps explain how the ecology, business, and economics of sport and commercial fishing are connected to the effects of climate change and how difficult it is to adapt to the resulting changes.

Can fisheries adapt?

The challenge now, says Pinsky, in a study in Oceanography, is for fisheries, which provide a source of protein to 60 percent of the world’s population, to adapt to these changes.

In the case of the black sea bass, for instance, the Atlantic States Marine Fisheries Commission, which regulates certain fisheries in the eastern United States, still allocates quotas among states according to their distribution in the late 1980s and early 1990s. At that time, black sea bass was more often caught in Virginia than in New York, while the bass is now found further north.

The regulations require that fish caught in North Carolina, for instance, be distributed and sold from North Carolina. While the number of black bass that can be harvested in North Carolina is the same as it was two decades ago, the black bass population has dwindled in those waters—forcing fishermen from North Carolina to travel to New Jersey to do their harvesting.

Fundamental changes are necessary for fisheries to remain healthy as changes in climate continue to affect the stability of marine life, Pinsky says.

While a number of species like the black sea bass are shifting their habitat range, not all species are moving at the same rate. Although it isn’t clear how this separation of predators will affect the food web in the future, it may force birds and mammals that rely on fish to survive to find new food and prey elsewhere.

“We don’t necessarily foresee a catastrophic collapse,” says Pinsky. “Species that are heavily overfished are especially sensitive to climate change, and so allowing overfished species to recover may be one of the best things we can do for preserving fisheries in the future.”

The US National Marine Fisheries Service funded development of the website.

Source: Rutgers