Leaving fish in the sea helps brake global warming

Fishing vessel

An interesting research paper has recently been published in Science Advances, which is co-written by Gael Mariani, a PhD student at Montpelier University France (he’s the lead author in the study). In perhaps my overly simplistic terms, he states that fish capture carbon and if they die in the oceans they take that carbon with them to the bottom but if they are fished the carbon is released into the atmosphere and as a consequence they make a massive contribution to global warming. It is therefore a good idea to leave the fish in the sea as a means to tackle global warming.

Fishing vessel

Fishing vessel. Fishing contributes to global warming. Photo: Joachim Müllerchen on Wikipedia.

Clearly you can’t stop fishing because you have to feed mouths, human mouths, but it’s a good argument to restrict fishing and as overfishing is well known it makes sense to think about restricting it in any case.

Specifically, the scientists say that when big fish die they act as a “carbon sink” by storing carbon dioxide in the ocean. When living they absorb huge quantities of the greenhouse gas which helps to regulate the amount of the gas in the atmosphere.

They hold onto this carbon when they die and come to rest on the bottom of the ocean. The scientists call this “blue carbon pump”. It is an aspect of global warming which has been overlooked to date. The analysis found that the activities of ocean fisheries has resulted in the release of at least 730 million tonnes of carbon dioxide since 1950.

In 2014, 20.4 million tonnes was discharged. This is the equivalent of 4.5 million cars. They say that the carbon footprint of fisheries is 25% higher than previously thought. To the release of carbon from fish you have to add the burning of carbon fuels by fishing fleets.

Interestingly, they say that mackerel, sharks tuna and swordfish are made up of 10 to 15% carbon. When the fish die and rest on the bottom of the ocean the carbon is trapped for thousands or even millions of years. It’s a huge mountain of trapped carbon which would otherwise have gone into the atmosphere. That is my interpretation. Mr Mariani is calling for “new protection and management measures [to] be put in place”.

My thanks to The Times of Nov 2nd.