LONDON -- The seas around Britain are starting to teem with fish species once deemed exotic as climate change raises water temperatures, forcing the former dominant occupants to flee northward toward the Arctic and opening the way for those from the hotter south, according to marine and fisheries scientists.
Such is the extent of the migration already observed, which is expected to grow in coming decades and could even force a change in the country's fish menus. Once-local species are moving farther afield and therefore becoming more expensive to catch, while formerly foreign ones become plentiful locally and therefore presumably cheaper and easier to harvest.
"People have started calling the North Sea the crucible of climate change. It has warmed by about a degree Celsius over the last 50 to 100 years, which is something like six times faster than pretty much any marine area around the world," John Pinnegar, program director of the Marine Climate Change Centre at the government's Centre for Environment, Fisheries and Aquaculture Science, told ClimateWire.
"We have seen quite a lot of warm-water fish becoming more abundant -- things like anchovy, red mullet, sea bass -- all of which are actually quite nice to eat," he said. "Species that we traditionally got in the Bay of Biscay area are now showing up in the Irish Sea and into the North Sea. At the same time, things like cod, a cold-water fish, seem to be suffering and moving northward.
"The British have very traditional fish eating habits -- historically consuming predominantly cod in the south and haddock in the north. Not many people are used to eating red mullet and sea bass. But eating habits can change, and that is partly what adapting to climate change could mean," he added.
Pinnegar said sea bass not only has quadrupled in quantity in the seas off southern England in the past 20 years, but is now being found by anglers as far north as Scotland and is being commercially fished off the coast of Yorkshire, 250 miles north of its former northernmost range.
The chips remain, but the fish are foreigners
Pinnegar was lead author of the marine and fisheries section of a vast U.K. government report earlier this year on all aspects of the risks associated with climate change. Among other findings, the report shows significant warming of waters around the United Kingdom in studies from 1961 to 1990 across all seasons but particularly marked in autumn and winter.
Although the picture is complicated by factors such as the impact of commercial fishing, water-based recreational activities and the growth of human coastal populations, scientists say the rising acidity of the seas due to absorption of carbon dioxide from the atmosphere and changing salinity and oxygenation is having an effect on fish and shellfish.
"Sea temperatures are rising -- although it is hard to say whether this is a blip in geological terms or evidence of global warming. But with it we would expect to see some changes in the species distribution of fish," said Richard Handy, director of the Ecotoxicology Research and Innovation Centre at Plymouth University's School of Biomedical and Biological Sciences.
"As the seas warm, we would expect to see some of the species of fish we more usually associate with the warmer waters off Spain to start appearing in the U.K. There have even been reports of fishermen catching barracuda and types of shark they haven't seen before," he added.
Fish food moves north, too
While some of the colder-water species will move north to escape the heat, the rising water temperatures could also have an impact on those that remain as their metabolisms speed up with the warmth and they need to eat more. Meanwhile, the plankton and other species lower down the food chain have already moved on and so become scarcer.