They are therefore carbon sinks - the size of which has never been estimated before.' 'As a result, most of the carbon they contain is sequestered at the bottom of the sea for thousands or even millions of years.

'When these fish die, they sink rapidly,' Prof Mouillot said. Large fish such as tuna, sharks, mackerel and swordfish are about 10 to 15 percent carbon. 'And now we know that extracting fish releases additional CO 2 that would otherwise remain captive in the ocean.'

'Fishing boats produce greenhouse gases by consuming fuel,' Prof Mouillot said. An estimated 20.4 million metric tons of CO 2 was emitted in 2014 - equivalent to the annual emissions of 4.5 million cars.Ĭo-author Professor David Mouillot from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (CoralCoE at JCU) and the University of Montpellier said the carbon footprint of fisheries is 25 percent higher than previous industry estimates. Mr Mariani led a world-first study showing how ocean fisheries have released at least 730 million metric tons of CO 2 into the atmosphere since 1950.

'But when a fish is caught, the carbon it contains is partly emitted into the atmosphere as CO 2 a few days or weeks after,' said Gaël Mariani, a PhD student at the University of Montpellier in France. This is a form of 'blue carbon' - carbon captured and stored by the world's ocean and coastal ecosystems. When a fish dies in the ocean it sinks to the depths, sequestrating all the carbon it contains with it.

When was fishing in the dark released