Leaving more big fish in the sea reduces the amount of carbon dioxide (CO2) released into the Earth’s atmosphere, new research has found. Ocean fisheries have released at least 730 million metric tons of CO2 into the atmosphere since 1950.
When a fish dies in the ocean it sinks to the depths, sequestrating all the carbon it contains with it. This is a form of ‘blue carbon’, or carbon captured and stored by the world’s ocean and coastal ecosystems, explains a statement.
“But when a fish is caught, the carbon it contains is partly emitted into the atmosphere as CO2 a few days or weeks after,” explains Gaël Mariani, a PhD student at the University of Montpellier in France who led the new study into ocean fisheries.
An estimated 20.4 million metric tons of CO2 was emitted in 2014 by ocean fisheries – equivalent to the annual emissions of 4.5 million cars.
Large fish such as tuna, sharks, mackerel and swordfish are about 10 to 15 percent carbon, and when they die, they sink rapidly. They are therefore carbon sinks, say the researchers.
The authors also say the phenomenon has not only been overlooked until now, but it happens in areas where fishing is not economically profitable: in the Central Pacific, South Atlantic, and North Indian Oceans.
“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.
For the authors of the study, the new data strongly supports more reasoned fishing.
Photo credit: Flickr Creative Commons