People’s taste for seafood affects a surprisingly large share of Earth’s oceans. That’s according to a new study that mapped where marine fish are harvested.
Oceans cover more than two-thirds of the planet’s surface. In 2016, fishing fleets used more than 55 percent of the ocean’s area, the new study shows. In contrast, only about one-third of Earth’s land area supports agriculture or livestock grazing. That means that catching fish uses four times as much of the Earth’s surface as all the food plants and animals grown on land!
Fishing vessels have plied the oceans for hundreds of years to catch fish. Data about where they fished and how much time they spent at sea have been scarce and inconsistent. Now, though, most large ships have a tracking system. It’s meant to help them avoid collisions. Called an automatic identification system, or AIS, it sends out data on where vessels are and how fast they are moving.
Fourteen researchers from universities, Google and other groups used these data to map fishing throughout the seas. For their new study, they examined 22 billion AIS data points between 2012 and 2016. The team trained computers to sort through all of those data. They turned up more than 70,000 fishing vessels. Then, the researchers tracked the ships’ activity — their time at sea. The researchers reported the results February 23 in Science.
Much fishing takes place close to coastlines. This isn’t surprising, because countries can claim exclusive rights to fish in waters closest to their own shores.
A few fishing hot spots were farther out in the open ocean, the team found. One such spot was the northeastern Atlantic Ocean, around Europe. Others were off the coasts of South America and West Africa. In those areas, cold, nutrient-rich water rises toward the surface from the deep ocean. The nutrients in that upwelling water helps nourish large populations of fish.
Surprisingly, just five nations dominated those fishing spots in the open ocean. China, Spain, Taiwan, Japan and South Korea accounted for nearly 85 percent of this fishing on the high seas. The affected areas do not belong to any one country. This means that they can be especially vulnerable to overfishing.
Understanding the extent of ocean fishing is important, the researchers note. So is knowing how fishing varies over space and time. This information might help identify spots that need protection. And it could guide international efforts to safeguard fish populations. That may be particularly important in a time of rapid ocean change. For example, ocean water temperatures are rising. This has caused some fish populations to migrate to new sites. Meanwhile, fishing activity on the seas has also been increasing.