Commandeer the ships and auction them off for scrap at home. Arrest and charge the fishermen.
If they flee, sink the ship.
They’ll catch on.
If they flee, sink the ship.
They’ll catch on.
So how about:
Sell the ship, let the crew live in a nice hotel, book them a 1st class flight back home, then bill the country under who's flag the ship was operating. If they can't / refuse to pay, import sanctions.
That way, you're not punishing the crew, yet making such behavior financially uninteresting. That's the only way because the person who decided to send that ship there is probably far away and busy counting profits.
Also, it's a lot easier to capture the boat if that's a positive experience for the crew. They might flee from a trip to prison but few people run from a paid vacation offer.
They may still run if accepting the paid vacation offer would be followed by imprisonment at home.
So offer them permanent residency instead. And then prepare for the logistics issue of managing a great fleet of boats racing straight to your ports.
"Dealing" with China is going to get a lot hotter. Period.
Want to get rid of the fishing fleet? Make a credible offer of residency and amnesty to all their crews - no strings attached, no continued use as pawns in politics. Simple trade: they bring in and surrender their vessel, you give each a green card, a key to a room, some starting cash, and a "thank you for your service", and forget about them.
But OK, so let's scratch the "and forget about them" part. Have the counterintelligence agency keep their details in their database, and warn them that they won't get security clearance in the next decade or three. This won't discourage anyone who's eager to escape their home country.
Or start using a bunch of them to sink for reef seeding.
The point is to make the expected ROI of trespassing in other nations' territorial waters negative. The crew is cheap and easy to replace relative to the boat. So you have to make the boat go away (sink it or impound it) to make the corporate owner back on land feel the heat.
Imprison them and give them back to their home country ASAP is probably the right way to handle the crew.
It would also have the nice side effect of dissuading countries to lend their flag to shady companies all over the world.
Realistically, once this becomes a strategem, and a known one, anyone with a boat can enter your waters, hoist the jolly roger, then say "Yeah, take me into asylum." And poof, your immigration procedures evaporate.
Aren't the vast majority of these actually "flags of convenience" and registered in Panama?