Subtropical Species Replace North Sea Cod As Water Warms - Independent

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"Cod and other coldwater fish in the North Sea and North Atlantic could soon be replaced by subtropical marine species such as tuna, sharks and sea horses lured by warmer waters caused by climate change.

One of Britain's leading marine scientists has warned that a minor change in temperature of the seas off the north-west coast of Scotland and the rest of the UK is having a dramatic effect on traditional marine life. The once-thriving cod stocks, depleted by over-fishing, are being replaced by tuna, red mullet, horse mackerel, pilchard, squid, john dory, sea horses and leatherback turtles. Martin Angel, a government adviser and chairman of a steering group investigating marine productivity, said close examination of the tiny zooplankton species Calanus finmarchicus, which provides a vital food source for young cod, salmon and other coldwater species, shows it is being driven further north as the seas around Britain warm.

"Calanus finmarchicus used to be extremely abundant in the North Sea," Dr Angel said. "If you dipped a plankton net into the waters off Britain it would make up about 80 per cent of what was caught. But as the seas warm, the whole ecological system is changing; plankton more usually associated with southern waters takes over and the species of fish which feed on it expand their traditional territories."

Dr Angel said the largest change has been in the past 15 years, and that within 10 years tuna could be almost as common in Scottish waters as cod. "These subtropical species have been migrating north at a rate of 50 kilometres a year," said the scientist who wrote the last Oslo and Paris Convention report into the health of the Atlantic and North Sea and who was the UK chairman of the International Year of the Ocean."

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http://news.independent.co.uk/uk/environment/story.jsp?story=513250