The global fishing fleet is so big it can be seen from space, according to the University of California-Santa Barbara (UCSB), which reported that fishing activity now covers at least 55% of the world's oceans — four times the land area covered by agriculture — and can now be monitored, in nearly real time, to the level of individual vessels.

In fact, 70,000 vessels of the global fishing fleet traveled 460 million km in 2016, which is equivalent to traveling to the moon and back 600 times, UCSB said.

Using satellite tracking, machine learning and common ship-tracking technology, scientists from UCSB teamed up with colleagues at Global Fishing Watch, National Geographic Society's Pristine Sea project, Dalhousie University, SkyTruth, Google and Stanford University to illuminate the extent of global fishing — down to single vessel movements and hourly activity. Their findings appear in the journal Science.

"I think most people will be surprised that, until now, we didn't really know where people were fishing in vast swaths of the ocean," said co-author Christopher Costello, a professor at UCSB's Bren School of Environmental Science & Management. "This new real-time data set will be instrumental in designing improved management of the world's oceans that is good for the fish, ecosystems and fishermen."

While the data set is hundreds of times higher in resolution than previous global surveys, UCSB said the total area of the ocean fished is likely higher than the 55% estimated. That's because some fishing efforts in regions of poor satellite coverage or in exclusive economic zones with a low percentage of vessels using the automatic identification system (AIS) were not included.

The team used machine learning technology to analyze 22 billion messages that were publicly broadcasted from vessels' AIS positions between 2012 and 2016 to answer the question, "What drives commercial fishing behavior?" Based solely on vessel movement patterns, the Global Fishing Watch algorithm was able to identify more than 70,000 commercial fishing vessels, the size and engine power of these vessels, what type of fishing they engaged in and when and where they fished, down to the hour and kilometer.

This new global view of fishing draws on advances in satellite technology and big data processing, UCSB said.

More than 40 million hours of fishing activity were observed in 2016, and while most nations appeared to fish predominantly within their own exclusive economic zones, China, Spain, Taiwan, Japan and South Korea accounted for 85% of the fishing observed on the high seas.

"This data set provides such high-level resolution on fishing activity that we can even see cultural patterns, such as when fishermen in different regions take time off," said co-author Juan Mayorga, a project scientist in the Sustainable Fisheries Group at the Bren School and with the Pristine Sea project. For example, China's fishing fleet is the largest in the world, but during Chinese New Year, fishing activity is reduced to levels comparable to those during seasonal bans enforced by the government.

The investigative team also found that when and where fishing occurs are tied more to politics and culture than to natural cycles such as fish migrations and marine food production. "Our analysis demonstrated that policies, cultures and economics play a huge role in driving fishing behavior," Costello said. "In addition, we examined whether fishing diminished when fuel prices were high and found a weak response. These are the kinds of things about which we've always speculated but haven't ever been able to test — until now."

The resulting interactive map — which is freely available to the public — shows a nearly real-time view of the fishing patterns of individual vessels and fleets, UCSB said. This allows anyone to see what is going on and to observe where policy boundaries are in place and where they are not.

"By making this data public, we are providing governments, management bodies and researchers with the information needed to make transparent and well-informed decisions to better regulate fishing activities and reach conservation and sustainability goals," Mayorga said.

The study not only opens a gateway for improved ocean management but also confirms that fishing activity is clearly bounded according to differing management regimes, which indicates the role that well-enforced policy can play in curbing overexploitation.

"This collaboration opens up myriad research opportunities," Costello explained. "We are leveraging the products developed by Global Fishing Watch to address new and important research questions that will improve fisheries sustainability around the world."