I would say NO, even though I have no experience with Lionfish. I doubt it's possible to get any concrete data on what % of total Lionfish that are say, off Florida's East Coast have been or can be killed by divers. I figure divers can mess up two things: Busting up living coral (as it is general knowledge that coral is dying at an alarming rate worldwide by other factors). Also, divers can mess up reefs by taking stuff off them (shells, fish, dead coral, etc.) at heavily populated dive sites. This may mean the particular site is now not as attractive for future divers, though it probably has little or no effect on total populations--probably much like divers killing Lionfish. But aside from those two things, I think any action by divers regarding Lionfish or any other aquatic life is like a needle in a haystack compared to the global situation (ei. pollution, commercial fishing, etc.). In this case as in others, "think globally, Act globally".