Most sharks live in tropical and temperate inshore waters. Relatively few live in Arctic and sub-Antarctic waters, the open sea and water deeper than 2km. All sharks are predators. The diet of different species ranges from tiny crustaceans to large fishes, other sharks, rays, dolphins, seals, sea birds and marine reptiles. Sharks may also scavenge, but most eat live animals.
All sharks reproduce by internal fertilization.
Rates of reproduction are low, with most species producing fewer than 20 young per litter, compared to fish which may produce thousands of young each season. The gestation period may be as long as two years. These low rates of reproduction, long gestation periods and the increasing threats to sharks mean that their survival is increasingly threatened. Hopefully this will lead to general conservation of cartilaginous fishes. As yet in South Africa, there are no quotas on cartilaginous fishes, while there are very strict quotas on bony fishes, e.g. pilchards.