Leading article: Troubles as deep as the oceans lie ahead

Another celebrity cook is attempting to get the public to take a closer interest in where our food comes from and how it is produced. Hugh Fearnley-Whittingstall has launched a campaign to draw attention to the practice of fish discards by European fishing fleets.

He has chosen a suitably scandalous target. Hundreds of tonnes of dead fish – up to half of all stock landed by some estimates – are ditched back into the ocean by fishing fleets each year so that they do not breach their catch quotas set under the European Union's Common Fisheries Policy. The waste is jaw-dropping and inexcusable.

Yet fish discard itself is merely an egregious by-product of a fundamentally broken system. The idea that the sustainability of the Continent's fisheries can be safeguarded by national governments meeting in Brussels each year to set quotas for their respective fleets has been tested to destruction. For decades, the quotas have been fixed not according to scientific guidance on what is sustainable, but haggling between national governments, all desperate to return with the best deal for their domestic fishing industries.

The consequences have been disastrous. A research paper from the EU Commission admitted last year that a majority of Europe's fish stocks are over-exploited and that almost a third have collapsed. Unless European governments take action, the continent's fisheries will go the same way as Canada's Grand Banks, whose once-thriving populations of cod have been fished to extinction.

The entire EU quota system needs to be dismantled and replaced with designated non-fishing zones that allow stocks to recover. Politicians across the continent will need to summon the courage to explain to angry fishing communities that this enforced moratorium is in their own best interests. That is the only way to end the scandal of discarded fish. Indeed, it is the only way to ensure that there are any stocks left in European waters over the longer term.

Overfishing is the classic tragedy of the commons. Since no single nation "owns" the high seas, they exploit it without restraint and without thought to sustainability. And this is not just a European problem. A comprehensive study in 2006 by ecologists from a dozen research centres around the world showed that, on present trends of overfishing around the world, the oceans will be entirely denuded of wild fish by the middle of this century.

It is true that cod stocks have improved in the North Sea somewhat of late thanks to EU quotas and catch regulation, rising from an estimated 37,400 tonnes in 2007 to 54,250 tonnes this year. But those stocks are still terribly low by historical standards. And the scientific estimate for the size of the stock required for a recovery is between 70,000 and 150,000.

And globally, we are still headed in the wrong direction. A new study in Science shows that mankind is extracting a greater volume of fish from the world's seas than ever before. The research also casts doubt on the manner in which scientists have been measuring the sustainability of fisheries. The depletion of wild fish stocks could be even more advanced than previously feared.

Meanwhile, demand for fish is rising. With a growing global population, the pressure on wild fisheries is likely to increase over the coming decades. Climate change will not help either, with a warming ocean expected to put marine ecosystems under additional pressure. Discarded fish is only the most visible sign of our thoughtless degradation of marine life. We are on an unsustainable course and if we do not change direction, we will arrive in a world of barren oceans.