Original Message

Solution:

autonomous ROV units like the mars rovers....that just swim around wrecks and structures armed with a hawaiian sling with a blade that chops their lil heads off instead of sticking them with a trident.

No mess to clean up because other fish with make quick work of the carcasses. 

A hunter seeker type robotic drone that just motors around all day/night killing, could even program it to drive itself into a docking station to recharge it's batteries when it get's low.

Someone needs to build this.  Hundreds, thousands of them.

Elon Musk, I'm looking at you.