In a paper published in Nature, Fernando Paolo, David Kroodsma and their team at Global Fishing Watch (with collaborators at multiple universities) analyzed two petabytes of orbital imagery from 2017-2021, identifying millions of vessels at sea and cross-referencing them with reported and known coordinates for vessels tracked via AIS.

What the study documents is that around three-fourths of all industrial fishing vessels are not publicly tracked, and likewise almost a third of all transport and energy vessels. The dark fishing industry is huge — perhaps as big again as the publicly documented one. (The imagery also counted increases in wind turbine and other renewable energy placements, which can be similarly difficult to track.)

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“Fish are an important dynamic resource that move around, so openly tracking fishing vessels is fundamental for monitoring fish stocks. It is difficult to understand and map the full ecological footprint of vessels without all of them publicly broadcasting their positions and activity,” said Paolo.

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If you were to count based on AIS data, you’d find that about 36% of fishing activity was in European waters, and 44% in Asia. But the satellite data completely contradicts this, showing that only 10% of fishing vessels are in European waters, and a staggering 71% in Asian waters. In fact, China alone appears to account for some 30% of all fishing on the planet!

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Our mapping can also reveal potential hotspots of illegal fishing activity. Previous work showed substantial illicit activity in the eastern waters of North Korea28, but our global mapping shows that most of the undisclosed fishing actually occurred in the western part of the Korean Peninsula (Fig. 2). In fact, this location showed the highest density of fishing vessels in the world from 2017 to 2019, with about 40 vessels per 1,000 km2. This previously unmapped activity peaked each year in May, during China’s moratorium on fishing in their own waters (Extended Data Fig. 6), and activity abruptly fell by 85% during the COVID-19 pandemic when North Korea shut its borders. Numerous fishing vessels not publicly tracked were also detected inside many marine protected areas (MPAs). For example, two of the most iconic, biologically important and well-monitored MPAs in the world—the Galápagos Marine Reserve and the Great Barrier Reef Marine Park—showed, on average, more than 5 and 20 of these vessels per week, respectively (Extended Data Fig. 7).