I've seen those studies on cleaner wrasses and reefs. My only issue with them is that no one has done studies to show how quickly they repopulate. In fact, IIRC, one study had a hard time keeping new cleaners out of the area for their study. Proving a reef without cleaner wrasses ever again is not what happens with fish collecting, AFAIK. Cleaner wrasses, AFAIK, don't have a fecundity issue whatsoever. So suggesting that taking cleaners is any different than taking an algae eating fish, or any other fish that provides a "service" to the reef, for example, is a little flawed, IMO.