Not sure the rules but they have crab trap roundups in SE La. They give a notice to the crabbers and any traps not picked up past the date are getting picked up. In one sense the they are 'constant killers' in that the crabs get in there die and then the fish get in there to eat the dead crabs, die, then crabs eat the fish, etc. BUT, the ones that have been there awhile seem to have sediment and mud all around them and vegetation growing out of them. I almost think that you could use them for restoration work as long as you allowed for the crabs/fish to get out. Eventually they would rust out and all you are left with is a patch of vegetation = new land

I don't know probably too easy and simple