To the moon and back

Global fishing efforts are so wide ranging that fleets covered more than 460 million kilometres in 2016 — a distance equal to going to the moon and back 600 times.

That startling revelation is contained in a newly published study in Science that quantifies fishing's global footprint for the first time.

"I've been working on fishing for 20 years and it totally blows me away," co-author Boris Worm, a marine biologist at Dalhousie University in Halifax, said of the findings.

The study — which included researchers from Global Fishing Watch, National Geographic, Google and U.S. universities such as Stanford — used satellite feeds and common ship tracking technology known as the automatic identification system (AIS).

It found that commercial fishing covers more than half of the ocean's surface: "Our data show that industrial fishing occurs in 55 per cent of ocean area and has a spatial extent more than four times that of agriculture," the study says.

Most nations appear to fish predominantly within their own exclusive economic zones, but fishing fleets from China, Spain, Taiwan, Japan and South Korea accounted for more than 85 per cent of the observed fishing effort on the high seas.

"The fundamental problem with fishing is the lack of oversight particularly on the high seas," Worm said. "Now we have that oversight — we can see it from space."

The study found some larger fishing vessels undertake surprisingly lengthy travels, he said.

One Japanese vessel leaves its home port to fish off South Africa before moving on to West Africa, then transits the Panama Canal and fishes in the eastern tropical Pacific before returning home.

"I've never had data on it, so now I can actually track single voyages that go straight around the globe," Worm said.

Researchers captured the activity of more than 70,000 vessels, including about 75 per cent of industrial fishing vessels longer than 36 metres, by using 22 billion global AIS positions from 2012 to 2016. They point out the figures represent a small proportion of the world's estimated 2.9 million motorized fishing vessels.

Global fishing hotspots include the northeast Atlantic and northwest Pacific as well as regions off South America and West Africa.

The study found areas of minimal effort in the Southern Ocean, parts of the northeast Pacific and central Atlantic and the exclusive economic zones of many island states "forming conspicuous holes in the global effort map."

The number of areas fished globally is likely even higher, the researchers said, given many regions have poor satellite coverage and a lower percentage of vessels using AIS.

Longline fishing was the most widespread activity and was detected in 45 per cent of the ocean, followed by purse seining at 17 per cent and trawling at 9.4 per cent.

Longliners had the greatest average trip length between anchorages — 7,100 kilometres.

Worm said the study found that fishing wasn't disturbed by significant weather events or by such things as the price of fuel.

"They just go out and fish," he said. "I think oftentimes because they are operating, particularly on the high seas, at the margin of profitability they just have to keep those boats running."

David Kroodsma, director of research and development for Global Fishing Watch, said the over-arching goal of the study is to create transparency for an industry that has had little in the past.

Kroodsma said it's hoped the data can be used to improve fisheries governance around the world. He said the global map it produced is hundreds of times higher in resolution than "anything we've had before."

"For me what's most exciting is not just this dataset but what comes next. There are all of these questions about how we fish in the ocean that we can now answer that we could not before," he said.

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