North Sea cod: Is it true there are only 100 left?

If recent reports are to be believed, the North Sea cod's days are numbered. But should we believe these reports? What do the experts say about the numbers of fish that are left?

The Daily Telegraph recently ran the headline: "Just 100 cod left in the North Sea". It sounded fishy. Trawlermen were furious.

"It just makes my blood boil - 100 cod in the North Sea?" fumes Brian Buchan, who's been fishing in the North Sea for more than 30 years. "More like 100 million cod in the North Sea."

It's not a trivial issue. Over-exploitation and conflicts over fisheries cause major problems worldwide.

The story was picked up by other media, including the Atlantic Wire and Canada's Globe and Mail, but it started in the The Sunday Times which reported there were "100 adult cod in North Sea". A different claim - but still wildly wrong.

The newspaper got the figure by looking at data from the International Council for the Exploration of the Sea (ICES).

It then asked researchers from the British government's Centre for Environment, Fisheries and Aquaculture Science (Cefas) for help with the numbers. According to Cefas, however, the journalists "misunderstood the data".

The Sunday Times chose to class an adult cod as aged over 13. But that's not merely an adult cod. It's an ancient cod.

"Cod start to mature at ages one and two and they're fully mature by six," says Dr Carl O'Brien, the UK's chief fisheries science adviser.

So we shouldn't be surprised that there are very few cod aged over 13 (in fact fewer than 60 have been recorded in the North Sea in past 30 years) just as we shouldn't be surprised there aren't very many humans over 100.

So where did the newspaper get the idea that cod reach adulthood at 13? Well in the same article, the Sunday Times stated that cod could live to 25, which implies a 13-year-old cod is merely middle-aged.

Dr Tom Webb, a marine ecologist, says this age comes from the website fishbase.org. He says that although it is a reliable source of fish-related data, the idea that cod in the North Sea live to 25 is a bit of a red herring.

"For each species it [fishbase.org] has a front page with some headline stats - for instance maximum age, which for cod is given as 25," he says. "But the estimate of 25 was not from a North Sea cod, it was from a cod in the Barents Sea. The only estimate for a North Sea cod of maximum age is 11."

All this raises a question. Given what we know about when cod mature, just how many "adult" cod are there in the North Sea? Remember, the Sunday Times said there were just 100. The right answer? Well, using the same dataset, the right answer appears to be rather more than 100 - 21 million, in fact.

A spokesperson for the Sunday Times told the BBC: "The headline and the first sentence of the article over-simplified a complicated issue, which we regret. However, the rest of the story made clear that we were referring to cod over the age of 13 and the figures cited were accurate."

And what of that other headline - "Just 100 cod left in the North Sea"? Looking at the data, it seems a more accurate headline would read "Just 436,900,000 cod left in the North Sea". Wrong by about half a billion, then, which is perhaps a new record for the most inaccurate headline ever covered by More or Less.

Trawlerman Brian Buchan was infuriated by the headlines because, he says, while there certainly was a problem with North Sea cod stocks in the past, the situation is rapidly improving. "We've seen more cod this year then we've seen for 30 years," he says.

Dr Carl O'Brien is more cautious but agrees that, contrary to the recent headlines, cod stocks are getting healthier.

"The latest international assessment shows there has been a gradual improvement in the status of the stock over the last few years. So although there's a long way to go, there are good indications that the stock is ready to recover."