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
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.
“The instance of leatherback turtles finding their way to
Dr Angel, who is based at the Southampton Oceanography Centre, said that within the next few years sea horses will be a common sight around the Scottish coast as will several species of sharks and john dory, an olive-green spiny fish more usually associated with continental shelf waters from south-east Queensland, south and north-west Western Australia, the western Indian Ocean, eastern Atlantic, Mediterranean and the waters of New Zealand, Japan and Spain.
“The rate by which john dory-like fish are advancing up the coast is incredible,” said Dr Angel. “Already they can be found off
“A squid fishery is developing off the coast of
The influx of new species is not necessarily good news for the beleaguered fishing industry. Dr Angel said: “It’s not just about replacing one species with another as these new species are not as productive as cod. Even if the fishermen could fish as much as they wanted they would never catch as much; there are just not the numbers to sustain that.”