> If that still isn't enough, shop around for small warships or gun boats. Or mount a gun pod on your planes. A rapid-firing 20mm cannon can do a significant am

> If that still isn't enough, shop around for small warships or gun boats. Or mount a gun pod on your planes. A rapid-firing 20mm cannon can do a significant amount of damage since they can use explosive shells. Yeah, you can pretty effectively and safely (to you) threaten un- or lightly-armed ships with a 1930s-vintage biplane. Don't need fancy or expensive equipment to do that, if you're willing to go so far as actually firing on violating vessels. A handful of cheap used Cessnas with light "dumb" bombs attached would probably be damn effective at getting fishing vessels to go away and not come back for a while, even—again, if you're willing to actually attack. It's got to be restraint, not cost, preventing damaging or sinking the violating vessels, even for fairly small nations.