Like I said, fish tacos. I'm pretty sure the lionfish don't eat the adult groupers
During my most recent trip to Hawai'i I asked which fish were good choices for spearing and eating. The guy I was asking said they (he and other locals) shoot just about anything including parrotfish and the state fish (a triggerfish with a long name). As much as I like to eat fresh seafood I don't think I could bring myself to shoot anything that may be endangered or simply is so beautiful that it makes the world a better place just by being there. When I was a kid (in the 60s) a spearfisherman who killed a 400 pound giant sea bass was held in high esteem. Now they are protected in California and sightings are fairly common in some areas. However, the water is so polluted in so many areas that I have doubts about very many species surviving into the next century except for perhaps the bottom-feeders. In any case apparently lionfish don't eat yellow-striped grunts and they are very abundant around Isla Mujeres. Humans must not like them either.