dinsdag 18 juni 2013
Facts about Whalesharks
The gentle giants of our oceans and seas has got to be whale sharks. The biggest ever whale shark reached an enormous 13 meters in length, and these amazing creatures are not only the biggest sharks we have in the whole world, they are biggest fish of any kind. The reputed maximum length of the fearsome great white shark only reached 7 meters, a dwarf in comparison. Not unlike humans, whale sharks have a lifespan of 70 years on average, and they spend their days gently swimming about in the warm and tropical oceans of the world, mouth open to filter feed from the plankton and microscopic organisms that float in our ocean's waters. Whale sharks are unperturbed by human activity, and even allow divers to hitch a ride. Their teeth are the size of match heads, and while no doubt their jaws could be powerful, they have never shown any aggression towards humans. Their teeth play no role in eating, as plankton does not need to be chewed. Scientists are still learning about this amazing creature. In 1996, a pregnant whale shark that was caught was found to be carrying 300 pups (the correct terminology for shark babies), and newly born pups measure up to 0.5 meters long. Not much is known yet about gestation length, but it is believed that female whale sharks do not reach sexual maturity until they are 30 years old. This is the age they have to be before they can mate and reproduce. Originating 60 million years ago, the whale shark has evolved little in that time. They, or their ancestors, must have been compatriots of the feared megalodon shark. Whale sharks are to be found in numbers in the warmer oceans of the world and they are largely pelagic, meaning they are ocean going and prefer the deep waters of the open oceans. They tend to travel alone. Several times a year they congregate together in certain spots (known as aggregating) where plankton is plentiful. Those areas where whale shark aggregation occurs are all within a 30° north or south latitude from the equator. So great a loss in numbers have they suffered, that whale sharks are now listed as vulnerable in the IUCN red list of endangered species. Measures have been started to be put in place by some countries, to protect the whale shark from annihilation. The Philippines, India and Taiwan have all banned the fishing, selling, importing and exporting of whale sharks for commercial purposes. However, the law does not seem to be effective because the hunting and killing of whale sharks still goes on today, especially in Taiwan and the Philippines.