yes, have seen this on a large scale thorugh contacts at the shark trust and also on a locl scale on the project i run in mozambique.
If we want to protect the marine environment (and sharks) we all love so much we need to focus on people. People who have choices and alternatives available to them will not choose to destroy the environment, it is generally a result of poverty. If you can tackle poverty and create opportunities, then you can begin to think about marine life.
A fisherman who can work with tourists will not be as relyant on catching sharks; children who have access to schooling will not have to fish to survive in the future if tourism provides another income stream (and generally a more lucrative one than fishing); bilingual local guides who have been trained and had access to education will not have to cut black coral from the reefs to sell to tourists; again it is people who do the damage on every level...locals and visitors.
the film 'shark water' coming out soon goes ito the issue further. check it out. the level is insane, reasonable estimates are that 100,000,000 sharks are being killed each year - bearing in mind we dont know how many sharks are in the sea, this could easily spell disaster for a number of species.
chris