Clarification: The headline of this article over-simplifies a complex issue. It refers to a fall in the number of fully mature cod over the age of 13, indicating that this is the breeding age of cod. In fact, they can start breeding between the ages of four and six, in which case there are many more mature cod in the North Sea. CEFAS, the government fisheries laboratory, says the cod stock remains severely depleted but has been gradually improving. We regret the over-simplification
FEWER than 100 fully mature cod aged more than 13 are left in the North Sea after decades of overfishing, government experts believe.
An analysis of catches at North Sea ports across Europe in 2011 found not a single cod over the age of 13. Mature cod start breeding at 4-6 but can live for up to 25 years and reach lengths of 6ft.
Scientists say the reduced life expectancy of cod is lowering birth rates and accelerating the fall in stocks. Cod become more fertile as they get older, so the scarcity of older fish is particularly serious.
Callum Roberts, professor of marine biology at York University, said: “Many industrial fisheries are now so intensive that few animals survive more than a couple of years beyond sexual maturity [age four, on average, for North Sea cod]. This means that there are fewer eggs and larvae to perpetuate future generations.”
Chris Darby, head of the team at Cefas, the government fisheries laboratory, that did the research, said: “Our latest assessments suggest in 2011 there were 600 cod aged 12 to 13 in the North Sea, of which about 200 were caught. None of the catches recorded at North Sea ports around Europe showed any fish aged 13 or over.
“Analysis of that data suggests there are fewer than 100 such fish in the whole North Sea.”
Scientists are calling for the North Sea cod quota to be slashed from 32,000 tons this year to 25,600 tons for 2013. In the early 1970s, catches reached more than 360,000 tons.
The parlous state of mature cod numbers in the North Sea emerged from the annual audit of 45 fish stocks carried out by countries across Europe. In England and Wales alone, about 500,000 fish were measured. While there were 191m cod aged one, there were just 18m three-year-old cod.
The study found there were 65,300 tons of cod aged over three years in the North Sea. In 1971, an unusually high point for cod populations, the figure was 276,000 tons.
Scientists have told politicians that 150,000 tons of adult cod should be the minimum target for stock restoration.
One problem facing scientists is that so many cod are caught when young that is impossible to tell what proportion might naturally live beyond the age of 20.
Britain has long recognised overfishing as a threat to many species, including cod, and responded partly by paying owners to decommission their vessels. Since 1996 the number of vessels has fallen from 8,700 to 6,500.
Barrie Deas, chief executive of the National Federation of Fishermen’s Organisations, said the rise in populations of cod and other fish in the 1980s had prompted a boom in new trawlers — which led to overfishing.
“The most effective measure in rebuilding fish stocks seems to be removing vessels from service by paying owners to decommission them,” he said.
For fishermen there is positive news — of a sort. One consequence of the decline in cod is a surge in their prey, such as scampi.
The original headline on this article has been changed and the first two paragraphs edited to clarify the reference to stocks of older fish.
