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Scientists expect climate change and warmer oceans to push the fish that people rely on for food and income into new territory. Predictions of where and when species will relocate, however, are based on broad expectations about how animals will move and have often not played out in nature. New research based at Princeton University shows that the trick to more precise forecasts is to follow local temperature change.
The researchers report in the journalScience the first evidence that sea creatures consistently keep pace with "climate velocity," or the speed and direction in which changes such as ocean temperature move. They compiled 43 years of data related to the movement of 128 million animals from 360 species living around North America, including commercial staples such as lobster, shrimp and cod. They found that 70 percent of shifts in animals' depth and 74 percent of changes in latitude correlated with regional-scale fluctuations in ocean temperature.
"If we follow the temperature, which is easier to predict, that provides a method to predict where the species will be, too," said first author Malin Pinsky, a former Princeton postdoctoral researcher in ecology and evolutionary biology who is now an assistant professor of ecology and evolution at Rutgers University.
"Climate changes at different rates and in different directions in different places," he said. "Animals are basically being exposed to different changes in temperature."
The researchers compiled survey data collected from 1968 to 2011 by American and Canadian fishery-research centers and government panels. The surveys recorded surface and bottom temperatures, as well as the complete mass of animals in nine areas central to North American fisheries: the Aleutian Islands; the eastern Bering Sea; the Gulf of Alaska; the West Coast from Washington to California; the Gulf Coast from Louisiana to Mexico; the Northeast coast from North Carolina to Maine; the coast of Nova Scotia; the southern Gulf of St. Lawrence; and the Atlantic Ocean east of Newfoundland.
Details of the surveys revealed that sea creatures adhere to a "complex mosaic of local climate velocities," the researchers reported. On average, changes in temperature for North America moved north a mere 4.5 miles per decade, but in parts of Newfoundland that pace was a speedier 38 miles north per decade. In areas off the U.S. West Coast, temperatures shifted south at 30 miles per decade, while in the Gulf of Mexico velocities varied from 19 miles south to 11 miles north per decade.
Animal movements were just as motley. As a whole, species shifted an average of 5 miles north per decade, but 45 percent of animal specific populations swam south. Cod off Newfoundland moved 37 miles north per decade, while lobster in the northeastern United States went the same direction at 43 miles per decade. On the other hand, pink shrimp, a staple of Gulf Coast fisheries, migrated south 41 miles per decade, the researchers found.
