Wednesday, July 10, 2013

Gentle Giants — Whale Sharks a.k.a. World's Largest Fish/Shark

Galapagos: Realm of the Giant Sharks

This is an early preview of a film we are making about an ambitious project to track and study the largest fish in the sea: whale sharks.

DID YOU KNOW? The Whale Shark gets its name from its size. It is the world´s largest shark, the world´s largest fish. Often confused with true whales which are mammals.

It may reach up to 60 ft in length and 50 - 60 tons in weight, although the average size of those visiting the Galapagos is between 35 - 45 ft and an estimated 30 - 40 tons.

To more accurately measure the sharks as they swim by we will be using an innovative but simple method of laser photogrametry (Rohner et al 2011). This is a novel technique used for measuring whales sharks by taking pictures while aiming them with two equidistant lasers mounted at each side of the camera. By photographing part of the animal at a right angle, the total length may be extrapolated. This study will give much more accurate data about how long are the longest fish!

No one has ever witnessed mating or the birth of a whale shark, but from data collected from dead sharks it is believed that they are ¨ovoviviparous¨ a term which means they give birth to live offspring, known as pups. The have twin birth canals which can contain up to 300 foetuses. it is thought that they may be around 3 ft at birth and may practice cannibalism, whereby the young prey on other young whilst still inside the mother!

Nothing is yet known about survival rates, growth rates, longevity, at what age the sharks reach sexual maturity or where the young spend their first years.

Whale sharks are plankton feeders, seemingly having little use for their array of over 3000 small teeth. They do however occasionally practice lunge feeding upon encountering fish schools, although the circumstances surrounding this behaviour are not clear.

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