Whatever their lifestyle, sharks and rays share some of the most interesting child-rearing habits in the world of fish. Unlike the many fish that lay millions of eggs at a time, sharks bear relatively few young. Some egg-laying species can have more than 100 pups at a time. In sharp contrast, the deep-sea sharks usually give birth to just one or two young. This slow reproductive pace, unfortunately, threatens the survival of some sharks.
Sharks are in danger of being overfished.
They live a relatively long time, reach reproductive age late in life, and then produce relatively few young. So it can take a long time to rebuild a population that has been overfished. Overfishing of some sharks is becoming a serious problem, Musick and other experts agree. But others are killed just for their fins or cartilage, which are considered potent medicines in some parts of the world. If nothing is done, researchers say, some species could become extinct within 50 to 100 years.