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The New Technologies That Could Slow the Slaughter of Sharks

Tens of millions of the top ocean predator are killed every year when they’re caught in fishing lines. Researchers tracked blue sharks to see how close they get to fishing boats whose locations are now mapped worldwide in an effort to detect illegal activity.

Written by Matthew O. Berger Published on Read time Approx. 5 minutes
A blue shark swimming off the Channel Islands in California.Mark Conlin/Courtesy of NOAA

Thanks to Global Fishing Watch, anyone with an internet connection can see the location of more than 60,000 fishing vessels across the world. Now conservationists are adding some new data to that mix, the location of sharks, in an effort to slow the inadvertent killing of tens of millions of a top ocean predator snared in fishing lines each year.

Environmental group Oceana on Thursday revealed the results of a pilot program that attached satellite tags to blue sharks off the northeast coast of the United States to track their movements. Researchers then overlaid that data on a map of fishing vessel locations created by Global Fishing Watch. Their aim was to demonstrate the role new technologies can play in identifying the overlap between threatened species and fishing activity to spur action to reduce bycatch.

“It’s an exciting new tool that we’re hoping will be useful for scientists and fisheries managers,” said Lora Snyder, an Oceana campaign director who works on the group’s shark program. “Basically, it’s just one of the first times that you’re seeing tagged shark data in addition to fishing data.”

The shark tracking effort is the latest effort to improve the usefulness of Global Fishing Watch. Launched in September 2016 as a collaboration between Google, Oceana and remote sensing company SkyTruth, Global Fishing crunches data on the location of commercial fishing fleets gathered from onboard transmitters to detect evidence of overfishing that has resulted in the decimation of fisheries worldwide.

Fishing also kills between 63 million and 273 million sharks each year, according to a 2013 study. In longline fisheries, which deploy miles of baited hooks, blue sharks account for 50 percent to 90 percent of the bycatch, a 2015 study found. Blue sharks are the most frequently caught shark in Canadian waters and the most frequently snared by U.S. longliners, according to 2011 and 2008 studies respectively.

“That’s why they were chosen,” said Snyder. Despite blue sharks’ relative abundance, there is uncertainty over how much impact bycatch is having on their populations, Oceana said.

But it’s about more than saving sharks. “Shark bycatch and depredation (damage inflicted on gear, bait and catch) complicates management of sharks and other species, and can undermine the operations and financial interests of the pelagic longline industry,” the 2008 shark study said. “Thus, deducing means to reduce shark interactions is in the best interest of multiple stakeholder groups.”

In June 2016, shark researchers from the environmental group Beneath the Waves and the University of Miami affixed satellite transmitters to the dorsal fins of 10 blue sharks in the northwest Atlantic and collected data on their location over a 110-day period. They then overlaid those shark movements with Global Fishing Watch’s location data on the movements of fishing vessels over the same time period.


The scientists found four instances of the 10 sharks coming near longliners that were likely fishing at the time, the closest within about one-tenth of a mile (160m).

Snyder said the tools and technique could be used to overlay data from other species that might be sensitive to bycatch impacts, such as sea turtles in the Gulf of Mexico caught by shrimp trawlers. The intersection of fishing activity and these species’ locations could indicate hotspots where fishing should be limited at certain times. The data could also be used to identify places where modified gear that limits bycatch is most needed, she said.

“These conservation and management measures are most effective with high-quality information about the tagged animals’ locations and fishing activity,” Snyder said.

But the shark data comes from only 10 animals and was only transmitted when the sharks surfaced. Over the 110-day period in which the sharks were monitored, the most days a shark transmitted data was 68. And managers already have a range of tools to help determine when and where to restrict fishing to lessen impacts on non-target species, including long-term observations and records of bycatch rates.

There are no current plans to collect data on other species, Snyder said, though she hopes that Global Fishing Watch could include a feature in the future allowing researchers to add their own data to the interactive maps. “We’re kind of just putting this out there,” she said. “We just wanted to show how it works.”

Getting high-quality, useful data on sensitive species isn’t the only challenge Global Fishing Watch projects have faced. The maps rely on data from fishing vessels’ automatic identification systems (AIS), which international regulations require to be used by ships over a certain size. AIS devices transmit location data, from which estimates of a vessel speed and direction – and, possibly, whether it’s transiting or fishing – can be derived.

Researchers tag a blue shark in June 2016. (George Andreadis/Beneath the Waves)

But prior to the initiative’s launch, concerns were raised that vessels fishing illegally would simply turn off AIS, intended as a safety device, when they wanted. Most monitoring and enforcement agencies rely on data from vessel monitoring systems (VMS). Commercial ships operating in particular fisheries are required to install onboard satellite transmitters that send near real-time data on vessel location to law enforcement authorities. VMS is generally thought to be more reliable and tamperproof, though the data it collects is typically treated as confidential, shared only within companies or regulatory agencies.

Another concern was that untrained citizens studying the interactive maps might incorrectly interpret the data or not understand the complexities of vessel movement data or fishing laws.

But in the 14 months since its launch, the initiative appears to have made progress addressing those issues. “We are able to detect when a ‘blackout’ in AIS signals is likely to be intentional rather than the result of interference or an absence of satellites overhead,” said Kimbra Cutlip, a spokeswoman for Global Fishing Watch. Ships must have AIS activated when entering ports and analysts can review patterns of blackouts to determine if they are likely intentional.

Cutlip added that detecting whether a vessel is in transit or fishing “has been at the core of what we do since the beginning.” An algorithm analyzes vessel movements and can determine what kind of fishing a vessel is doing, she said.

Global Fishing Watch is incorporating more data sources into its product, she noted, including VMS data, which typically requires the consent of governments. Indonesia’s VMS data was added to the maps in June; Peru agreed to share its VMS data in September.

“This is a particularly important not simply on the technological grounds, but because of the commitment these nations are making to transparency,” Cutlip said.

Cutlip said she hadn’t reviewed the shark data yet but that there are “a variety of people using [Global Fishing Watch] to overlap fishing vessel behavior with wildlife migration patterns and core habitats.”

She added that the platform has also been used by researchers help expand Revillagigedo marine park off the west coast of Mexico and to determine that sharks from a vessel transporting the animals illegally in Ecuadorian waters had likely been offloaded from four other boats in the days before the ship was caught.

More innovations are ahead. Cutlip said a “gear” layer that uses algorithms based on vessels’ movements to try to determine what fishing gear they’re using will be added to the map within the next couple of months.

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