. >> craig bovim is a local inhabitant and a surfer. he leads a group of concerned citizens who believe that chum makes sharks associate people with food. bovim thinks that may be why a shark attacked him three years ago. he remembers it every time he looks at his hands. >> and i can't describe the fear that went through me then. i mean, it's everybody's worst nightmare, and it was busy happening to me. >> the king of sushi is no longer treated like royalty. it is scraped and planed and then cut up into blocks. the industry's ability to supply the global market with inexpensive sushi has stoked demand, and that's created a mediterranean gold rush. >> welcome to 60 minutes on cnbc. i'm steve kroft. precious commodities are, by definition, rare, valuable, and in high demand, and very often they're located in places that are difficult to reach and sometimes dangerous. this edition features stories that take us down into the world of sharks, deep into the heart of africa, and onto the high seas for a look at the dark side of big-time commer