The sharks life cycle is, for the most part, still relatively hidden from humans. Much of the aspects of mating, birth, and life remain a mystery to man that is slowly being unfurled through study and research.
Of the over four hundred species of shark, there are only a few that have been maintained in captivity for any length of time and these are the species that most of the “averages” discussed in research are based upon.
A shark gestates from nine months to two years. There are three methods that sharks gestate, which include the ovoparity method. This is when the shark lays eggs that are soft leather-like cases and screws the eggs into cracks and crevices that will protect the pups from predators. When the eggs are screwed into the crevice or crack, they get very hard and keep the egg in place until the pup is born.
Some sharks carry their eggs in the womb, called the ovoviparity method. When a pup hatches from the egg it feeds on the other eggs in the womb and the fluids, then is born fully developed and functioning. The viviparity method is the same as mammals. The pups are carried in a placenta, nurse and are weaned there and then are born and swim away from the mother.
If sharks were like other fish that lay several hundred eggs in a year and have hundreds of hatchlings, they would not be endangered. But, because fishermen kill between 30 and 100 million sharks each year over the world, there are over 80 species threatened with extinction. Sharks do not mate until they are in their teens and only have one or two pups every year or two. There is no regulation on the hunting of sharks and they do not have the time to procreate in the numbers that they are being killed.
A shark lives up to twenty-five years on average. But, remember that the statistics are very limited on what we know about the sharks life cycle. The Great White shark may live much longer than that. Researchers have been following a Great White in the wild for over twenty-five years that is still healthy and well. In addition, there are Whale sharks that scientists believe are at least one hundred years old in the wild.
The sharks life cycle has long fascinated Seiji Tadashi while studying sharks along the Eastern Seaboard of South Africa.