Fishing industry creates same emissions as 4.5m cars in one year, landmark study says

The fishing industry creates the same carbon emissions as more than 4 million cars annually, suggests the first global study to estimate how much carbon is stored in large fish stocks.

Large fish such as tuna and mackerel are 10 to 15 per cent carbon, much of which is released after they are caught, and which would otherwise be used to sequestrate carbon at the bottom of the ocean,  researchers at the University of Montpellier in France found.

They calculated that ocean fisheries released an estimated 20.4 metric tons of CO2 in 2014, equivalent to the annual emissions of 4.5million cars, when the loss of those carbon sinks was added to emissions from fishing boats.

In total, ocean fisheries have released 730 million metric tons of CO2 into the atmosphere since 1950.

That makes the carbon footprint of fisheries 25 per cent higher than previous industry estimates, researchers calculated.

"When these fish die, they sink rapidly," co-author Professor David Mouillot. "As a result, most of the carbon they contain is sequestered at the bottom of the sea for thousands or even millions of years. They are therefore carbon sinks - the size of which has never been estimated before."

The research does not calculate the potential for increasing overall greenhouse gas emissions if fish was replaced by other sources of protein, such as red meat, which also have a significant carbon footprint. The authors suggested one solution could be replacing fish with plant-based protein.

The authors also say that current fishing levels are unsustainable, and the worst impacted places, concentrated in the Central Pacific, South Atlantic, and North Indian Oceans, are unprofitable without government subsidies.

"Fishing boats sometimes go to very remote areas - with enormous fuel consumption - even though the fish caught in these areas are not profitable and fishing is only viable thanks to subsidies," Mr Mariani said.

Mr Mariani added that there was a level of fishing that would provide a compromise between providing food and sequestering carbon.

"In areas experiencing overfishing or with depleted fish stocks, protection measures would increase the amount of fish in the ocean," he said.

Charles Clover, the executive director of Blue Marine Foundation, said the study was "fantastically important".

"Every industry has to get to grips with its impact on climate change, and the fishing industry has been saying for a long time that they don't have one.

"These results should change the way we regard fisheries forever."