CARTILAGINOUS FISH

"The skeletons of sharks, skates, and rays are composed of cartilage rather than bone. The 800 or so species primarily inhabit the marine realm, but a few venture into freshwater. Although they have a reputation for being dangerous, only a handful of species pose a threat to humans and the majority are quite harmless. In fact, sharks and their allies are extremely beneficial. They are among the top predators in the food chain, thus their presence is critical for maintaining the balance of marine ecosystems. And, because they are not readily subject to infections, medical scientists expect to learn much from them that will benefit humans. Unfortunately, many species are under severe threat, from over fishing for food, as well as from wanton killing. Given their importance, conservation of these magnificent creatures is crucial."