On June 5, the United Nations announced that the Agreement on Port State Measures (PSMA) will go into effect after being ratified by 30 countries. This is the first legally binding international measure to stop what's known as "illegal, unreported, and unregulated" (IUU) fishing.
The idea is pretty simple: No matter where a boat goes out on the high seas, it has to come into some port eventually to offload its wares. So countries will try to catch illegal activity at the ports. Under the PSMA, fishing boats will have to give advance notice before entering ports in these 30 countries, sending along extremely detailed information about their activities, fishing licenses, and catch totals and type. Landings can only happen at ports well-equipped for inspections.
The countries that ratified the PSMA, meanwhile, are obliged to inspect suspicious vessels or turn them away entirely. That last part is important. If an illegal fishing ship can't actually land anywhere without hassle, it can't make money.