Could depend on the fish species in question? Lionfish for example is extremely invasive in the Southern USA, so environmental agencies have been encouraging people to eat them to curb their population, potentially making it a more ethical choice. I've been seeing it pop up more and more, but it doesn't seem to have caught on too much.
But we should definetly limit our consumption though when it comes to more threatened/overfished species. There's also some unethical fishing practices out there such as removing sharks' fins then stranding them, causing harm to cetaceans, and other environmentally destructive fishing techniques.
The only reason it hasn't caught on is because they are very difficult to catch (spear) and even more difficult to prepare (venom glands). They are unbelievably delicious, but even so, I'm not going to trust a chef a don't know to be sure he didn't pierce one of those glands while preparing it. I'll trust myself or one of my friends that I no for 100% certain can do it right. So even though a handful of restaurants were offering it in the Keys and Miami, you'll really see people catching it themselves and preparing it just to be sure.