No one really knows how many of the world’s seas are being fished by commercial vessels—some scientists say nearly all of them. But a new study, which uses satellite tracking data from more than 70,000 ships to create one of the most detailed global pictures to date, has come up with a much smaller range: between half and three-quarters of the world’s seas. Researchers decided to tap the vast amount of data generated by anticollision beacons on ships—some 22 billion messages from 2012 to 2016. In 2016 alone, these ships traveled more than 460 million kilometers—about five times the distance from Earth to the sun.
There were several obvious fishing hot spots—the South China Sea, and the coastal areas of Europe, East Asia, and South America. Together with activity on the high seas, they covered some 55% of the ocean surface, the researchers report today in Science. But because of poor satellite coverage, some areas of the ocean appeared to be virtually unfished. When researchers extrapolated fishing activity to those areas, they came up with a new number: up to 73%. That’s far less than a previous estimate of 95% of the oceans, suggesting that large areas could become marine reserves without much economic cost to fishing.