https://phys.org/news/2018-06-economics-fishing-high-seas.html

"The reason most fleets continue to operate in the high seas is that they receive government subsidies. Without subsidies and the forced labor some of them are known for, fishing would be unprofitable in over half of the high seas fishing grounds," said Enric Sala, National Geographic Explorer-in-Residence and lead author of the study.

Using Automatic Identification Systems (AIS) and Vessel Monitoring Systems (VMS), the researchers were able to track the individual behavior, fishing activity and other characteristics of 3,620 vessels in near-real time. Combining this information with the global catch data from the University of British Columbia's Sea Around Us project, the team was then able to determine how much effort the vessels expended, how large their catch was, and how much profit the catch generated.