卫星观测到捕鱼业对公海的影响

Until recently, scientists had trouble identifying what was causing large numbers of fish to disappear from the high seas.

Now they have an answer: human beings.

By using emergency signals from ships, scientists got what they are calling the first complete picture of commercial fishing worldwide. And a new study claims the effect is much bigger than researchers thought.

Major commercial fishing covers more than 55 percent of the oceans. The world's fishing fleet travels more than 460 million kilometers a year, according to a study in the journal Science. That is equal to three times the distance between Earth and the sun.

Five countries do 85 percent of high seas fishing. The five are China, Spain, Taiwan, Japan and South Korea.

Boris Worm, a marine biologist at Dalhousie University in Canada, called the fishing study "mind-blowing." Worm helped prepare a report on the findings. He likened industrial fishing to factories that are mass producing goods for people around the world.

The latest fishing information was taken from 22 billion ship safety signals sent to satellites orbiting the Earth. Before this, scientists had to use shipping records and observations, which were not always correct.

Ships are obeying no-fishing areas and times, although they do sail along the edges of marine-protected areas. The study noted a drop in fishing around holidays, including Christmas, New Year's and the Lunar New Year.

"The maps of global fishing in this report are sobering," said Douglas McCauley, a marine biologist who wasn't part of the study. He works at the University of California, Santa Barbara.

The top country for fishing is China. Of the 40 million hours that large ships fished in 2016, 17 million hours were by boats sailing under a Chinese flag, noted marine biologist Barbara Block. She is with Stanford University in California

"No longer is the ocean, especially the high seas – out of sight, out of mind," noted Jane Lubchenco in an email. She formerly led America's National Oceanic and Atmospheric Administration.

Lubchenco was not part of the study.

From 2012 to 2016, the researchers collected signals from boats. New laws require many ships to carry identification systems that every few seconds report their position to satellites as a safety measure.

Scientists then used computer programs to show where the boats were fishing, how they were moving, and what they were likely fishing for and how the fish were caught.

The information was then compared with log books from some ships and they were the same, Worm said. It also shows that in the high seas, there is a heavy use of long line fishing, which catches more of the top predators like tuna, sharks and whales.

Researchers said the findings could be used to better protect the oceans and keep fisheries alive.

Block said that for too long scientists failed to recognize that human activities have the biggest effect on the planet. He added we have to develop a better system or else we'll end up with a planet without Bluefin tuna and some sharks.

I'm Susan Shand.

The Associated Press reported this story. Susan Shand adapted the report for VOA Learning English. The editor was George Grow.