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.
The "average" often referred to when you read about sharks is based on the few species that have been studied in captivity. However, this is a very small percentage of the four hundred species of shark that live on the planet.
Sharks gestate from nine months to two years. The fish have three methods of carrying their young that are distinctly different. Some sharks lay eggs that are shaped like a leather bag and are screwed into a crack or crevice in protected areas of bays or the ocean floor. This casing gets very hard once is is in place and protects the pups, or baby sharks from predators.
Most of the pups are born by a ovoviviparity method. This is when the eggs are retained in the mother and after hatching the pups live on the other eggs and fluid in the womb until they are born. The pups are totally functional and fully formed when they are born. Only one or two pups survive and these are the most developed of the eggs that have been started. There are some species that also carry their pups in the womb and have a placenta just like a mammal. These sharks still leave the pups when they are born, but the pups are nursed and weaned in the womb before birth.
A reason that there are over eight species of shark are threatened with extinction is because there is no regulations to protect them. Sharks are not like other fish that lay a lot of eggs and have several hundred babies every few months. Some sharks do not reach maturity until they are in their teens and have one or two pups every two years. With 30-100 million sharks being killed each year, there is not enough time for the shark population to recover.
A shark lives up to twenty-five years on "average". But, remember when we talked about the way statistics on sharks are collected? No one really knows how long a Great White live or exactly what their life cycle is. There has been one Great White followed in the wild for 25 years that is still active. Whale sharks are living today that many researchers believe are over one hundred years old
The sharks life cycle has long intrigued Seiji Tadashi while watching sharks along the Eastern Seaboard of Southern Africa.
