Huge fleets of Chinese fishing boats have been caught stealthily operating in North Korean waters--while having their tracking systems turned off. The potentially illegal fishing operation was revealed through a combination of artificial intelligence, radar and satellite data. This story originally appeared on WIRED UK. A study published today in the journal Science Advances details how more than 900 vessels of Chinese origin (over 900 in 2017 and over 700 in 2018) likely caught more than 160,000 metric tons--close to half a billion dollars' worth--of Pacific flying squid over two years. This may be in violation of United Nations sanctions, which began restricting North Korea from foreign fishing in September 2017 following the country's ballistic missile tests.