Ah yes, i guess trawling would be really dangerous, and bottom trawling suicidal... which is an even bigger bonus to sea life than preventing overfishing.
Shame? it only benefits such a small area :D difficult to know which is more damaging.
You've hit on an interesting idea: anti-fishing mines. Maybe a bouyant explosive attached to a weight by a cable such that the depth is well below what a ship on the surface could interact with. Getting snagged in the net arms it to detonate when the ambient pressure drops to near atmosphere is it's being pulled on board...
Or, less lethally, and probably just as effective: Drop a bunch of concrete blocks on the sea floor designed to snag nets. You wouldn't even need that many to make fishing the area entirely unprofitable.
[0] > Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders [...]
[1] > A bottom trawl consists of a large tapered net with a wide mouth and a small enclosed end. The mouth of a trawl net has two weighted doors that serve not only to keep the net open, but also to keep the net on the ocean floor. These doors can weigh several tons. In addition to the heavy doors, the bottom of the net is a thick metal cable (footrope) studded with heavy steel balls or rubber bobbins that effectively crush everything in their path [...]
Seems like the gear is designed to withstand a lot of punishment. I think the risk of hauling up something truly nasty probably works as a better disincentive, also doesn't actually need to be everywhere to be enough of a risk. e.g "this area is off limits, and btw we planted a bunch of depth sensitive bombs at undisclosed locations designed to be snagged by trawler nets."
It would probably be very effective, but i suspect also a bit too radical ... i mean lets call them what they are: fishing IDEs :P
I still feel like a gnarly shaped block of concrete should at the very least be able to catch the net.
Still, if you were to go for explosives, I'd probably make them explode as soon as the net tugs on em, instead of waiting for it to reach the surface. Wouldn't want to kill and/or maim random fishermen if it can be helped.
Shame? it only benefits such a small area :D difficult to know which is more damaging.