In some cases, the controls came too late, but humans finally figured out that they were taking too many fish out of the ocean. So they put catch limits in place, selectively closed down some fisheries, and instituted catch shares. Catch shares?
Yep, that's the name for a system in which companies and people fishing effectively buy a share of the market. It's not a monopoly, but it can be very hard to get into.
Investigative journalist Lee van der Voo examined the system in the book The Fish Market: Inside the Big-Money Battle for the Ocean and Your Dinner Plate.
This interview from 2017 really opened our eyes to fishing practices on the oceans.