There may be nothing new under the sun, but beneath the sea is a different story. Scientists studying 28 years of data from the Atlantic Ocean have found that climate change is causing drastic changes in fish populations off the European coast—and that's bad news for cold-loving species like cod, which have fed generations of Northern Europeans.
The North Sea, a cold wind-swept patch of the Atlantic stretching from Scandinavia to the U.K., is warming four times faster than the global average. During the last 30 years, the roughly 2°F increase in mean annual temperature (the North Sea swings between 63°F and 43°F during the summer and winter) has had a profound influence on fish growth and survival, egg maturation, and the plankton supporting food webs and commercial fisheries.
British scientists analyzed 11 surveys, covering at least a million square kilometers of the European continental shelf, and more than 100 million fish, "to get the 'big picture' of how warming is affecting fish communities," according to Stephen Simpson of the University of Bristol, whose research appears in a recent issue of Current Biology. They found that 72% of common fish species had responded to rising sea temperatures. Most species—three out of four—were growing more abundant, and hake and dab had doubled, while catches of cold-loving species, including haddock and cod, dropped by half.
"We see many more southerly, warm-water species faring well on the European shelf than more northerly, cold-adapted species," said Simpson in a statement. "This means more small-bodied, faster-growing species with shorter generation times, and potentially more diversity." In other words, cod may be replaced by new species adapted to the warmth such as red mullet and John dory.
The findings, while new, were not wholly unexpected. Previous research predicted massive shifts in the world's fisheries as the oceans warmed slowly under the influence of climate change. And in 2009, Princeton University and British researchers estimated that fish distribution was likely to shift at least 40 km each decade as southern species overtook ranges of cold-water species. While Nordic countries such as Norway might see catches rise, developing countries in the tropics would suffer the most and some polar species could face extinction. Fish and chips, get ready to meet your maker.
[Image: Flickr user f10n4]