Fishing reduces carbon sequestration in the ocean, researchers report.

A fish that dies naturally in the ocean sinks to the depths, taking with it all the carbon it contains. Yet, when a fish is caught, most of this carbon is released into the atmosphere as CO2.

The researchers estimate that because of this overlooked phenomenon, carbon emissions from fishing are actually 25% higher than what, until now, was considered to come from fuel consumption alone.

What’s more, part of the carbon extracted from the oceans is in areas where fishing is not economically profitable in the absence of government subsidies.

Carbon is a major component in the molecules that make up living tissue. Large fish like tuna, sharks, and swordfish are composed of 10 to 15% carbon. When they die, they quickly sink to the deep sea. As a result, most of the carbon they contain is sequestered for thousands or even millions of years. They are therefore literal carbon sinks, the size of which has never been estimated before.

This natural phenomenon, a blue carbon pump, has been greatly disrupted by industrial fishing.

“When we catch fish for our consumption, we also extract the carbon in their bodies, a fraction of which would have naturally sunk to the bottom of the ocean where it would have otherwise stayed, sequestered for many years,” says coauthor Juan Mayorga, a marine data scientist at the University of California, Santa Barbara’s Environmental Market Solutions Lab.

Read the full article about carbon emissions from fishing by Harrison Tasoff at Futurity.