To incentivize them to stop you have to give them better options. In this case, teach a man to not fish with explosives and you’ll feed him for the rest of his life.
Why make excuses for greedy jackasses? Their ancestors didn't invent this 5,000 years ago and it's the "oNlY wAy they can survive." They fished without bombs once. Some guy realized this depraved method works, so now lazy people choose to do it so they can get money faster than the people fishing legitimately can. That's why it's illegal.