Whale Shark

Picture courtesy of Zac Wolfe

Happy Shark Week, Explorers!  To celebrate, this week's Creature of the Week will be a shark!  But which one should we feature?  There are after all over 350 species of sharks in existence today.  Well since this is one big week of jaw-some excitement, let's just choose the biggest one of them all!  And that is the Whale Shark.

The whale shark is most definitely not a whale.  The term "whale" applies more to the size of the shark than to the type of animal.  These sharks can grow up to 40 feet long and can weigh up to 47,000 lbs. 1 Though there is no conclusive data, scientists believe the lifespan of a whale shark could be up to 60 years. 2  Whale sharks are the largest fish in the world, and like other sharks, whale sharks are cartilaginous, meaning their skeleton is made of cartilage, not bone.  Cartilage is the same material that gives structure to your nose or ears.

Though whale sharks are the largest fish in the world, they eat some of the smallest things!  Whale sharks are filter feeders, though they feed differently from basking sharks. 2  While basking sharks rely on moving forward and letting the water drift into their mouths, whale sharks can use a suction method by which they actively "gulp" the water into their mouths or a ramming style in which they move forward to push water into their mouths, filtering the food out and using their gills to push the water out of their mouth. 2  Whale sharks have small throats, so they can't swallow anything too large.  Their diet, therefore consists of things such as krill, macro-plankton, fish and invert larvae, and other small invertebrates. 1

Whale shark breeding is very much unknown.  Because they are pelagic fish, long term study on their behavior is quite difficult.  In 1995, a female whale shark was caught and scientists found 300 pups within her, which indicated that these sharks are ovoviviparous, meaning they carry the eggs within them past the time of hatching, giving birth to live pups. 2  These pups are generally between 16-24 inches long when they are birthed. 1  Whale sharks are believed to mature when they are around 29 feet in length or so. 2 

Due to commercial fishing, whale sharks are listed as Vulnerable by the IUCN, though the actual population numbers are unknown at this time. 1 Despite protection in some areas, places in Asia still continue to fish these sharks. 1  Whale sharks have been known to predictably aggregate in certain places, which can make them easy for fisherman to hunt them. 2  However, the aggregation also has helped places to boost ecotourism and research, allowing divers to see whale sharks in their natural habitat in large numbers. 1 

Please read more about this amazing "whale" of a shark at the following links:
http://en.wikipedia.org/wiki/Whale_shark
http://www.flmnh.ufl.edu/fish/gallery/descript/whaleshark/whaleshark.html