Marine Biology
whale shark

Life Cycle of Whale Sharks



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whale shark
Trenna Sue Hiler's image for:
"Life Cycle of Whale Sharks"
Caption: whale shark
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Image by: Marcel Ekkel
© Creative Commons-licensed content requiring attributio http://www.flickr.com/photos/marcelekkel/4803634069/

The life cycle of a whale shark is a very long one compared to many of the animals on the planet. They have been estimated to live at least 100 years.

There is much about the whale shark that is still a mystery. No man has ever witnessed the mating rituals or birth of a whale shark. In fact, for a very long time it was believed that whale sharks were oviparous (meaning producing eggs that hatch outside of the body). This was based on the discovery of a solitary egg sack found in Mexico. In 1996, a fisherman killed a pregnant female whale shark near Taiwan. Over 300 embryos, ranging in size from 40 to 60 cm were found inside the shark. Some of them were still alive. This would mean that the eggs are hatched within the mother and the young born alive (ovoviviparous).

The belief is that the whale shark becomes sexually mature at about 30 years. There is no data on how often whale sharks mate or even how they find each other.

It is believed that the young and small whale sharks live in small groups until they are over four meters long. The could be because other than size, the whale shark has no defenses. They are rarely seen and the current school of thought is that they live and eat in very deep parts of the ocean until they reach a bigger size.

Since the whale shark grows to be twenty meters long and weigh over 20 tons, it has to spend a lot of time consuming food. The whale shark has a unique way of eating. It is a filter feeder. The giant fish pushes out the jaws and filters everything in its' path. It is called cross-flow filtration.

The water and its' contents are taken in and then discharged through the gills. Anything bigger than 2 to 3 cm becomes trapped against the dermal denticles. The dermal denticles work like a strainer. It allows the water and very small particles to pass and be expelled through the gills.

What is left behind is what the shark eats. Eventually whale sharks must clean out the trapped particles in the dermal denticles. This is done by coughing.

Although it is clear that whale sharks roam the oceans looking for food, very few migration patterns are recorded. They know where they may show up in the spring or other times, but the time in between is unaccounted for.

So it seems that the life cycle of the whale shark is basic living. They seem to prefer the tropic waters. They obviously mate. They eat and they roam the oceans. What a wonderful life!

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://www.mesa.edu.au/seaweek2005/pdf/infosheet05.pdf
  • InfoBoxCallToAction ActionArrowhttp://animals.nationalgeographic.com/animals/fish/whale-shark/