Okay maybe I'm prejudiced but my feeling is that if you're down there spear fishing you're not looking for little fish but the bigger ones which are the breed stock. Line fishing is much more hit and miss and on a percentage basis you're much less likely to be taking breed stock. Of course, you then run into those who keep every single fish they catch no matter how small or how many and that can only be remedied by regulations. That's not likely to happen until it's too late as been shown over and over again both in the sportfishing and commercial fishing realms.
I'm a firm believer in catch and release and slot limits instead of catch limits as the only way to sustainably fish. The problem is that by the time we set any kind of limits the stocks will be depleted, the fishing guides will be out of business and commercial fishing for many whose lives depend upon it will also become a thing of the past.
Look at the stocks from 10 or 15 years ago to today, where there used to be mass schools traveling the waters of AC there are virtually none. Commercial over fishing and all take sportfishing are major contributors. No, I wasn’t here back then but my closest friend was born on this island and her father has been a fishermen all of his life so my information comes from a reliable source.
I guess I just don't have faith that when faced with a big ass snapper that someone with a spear is not going to let loose. At least with hook and line the fish has a better chance at outwitting the angler IMHO.