Welcome to our post of images and video highlighting the threatened whale shark, the largest fish in the world.
Swimming with Whale Sharks – The Largest Fish in the World
Source : Miguel Hilario
The whale shark is a graceful, harmless giant of a fish which can grow to an incredible size during its lifetime.
As the largest fish in the world, mature adults reach the size of a school bus, but their diet is made up of mainly tiny plankton and fish eggs which they filter-feed on as they swim with their big mouths wide open. The whale shark is also the largest living non-mammalian vertebrate -its skeleton is entirely, made up of cartilage compared to other fishes whose skeletons are made up of bones.
The biological characteristics of this elusive giant make it very susceptible to over-exploitation. Its large size, long life and slow growth means that populations take a long time to recover from disturbances. While it is thought to have predators such as the blue shark, the blue marlin and the killer whale, the main threat to the whale shark is man’s commercial fishing activities.
The whale shark is both the biggest shark and the biggest fish. Its name may be misleading because it is not a whale.
They are massive creatures, reaching lengths of 12 meters or more, and weigh more than 21 tonnes. Contrary to other sharks whose mouths are on the underside of the head, the whale shark’s mouth is at the tip of the snout, and can stretch almost as wide as its body.
Its head is wide and flat; it has small eyes, two dorsal fins on its back, five large gill slits and two pectoral fins. Like our fingerprints, each whale shark has a unique white spots pattern, making it possible to indentify individual sharks. Researchers usually take their photos then use specialized computer mapping software to identify them.
Habitat and Ecology
The whale shark is widely distributed around the world and can be found in the waters of more than 100 countries. It occurs in all tropical and temperate seas, with the exception of the Mediterranean. This means that it can be sighted throughout the Atlantic, Indian and Pacific Oceans as well as the Red Sea and the Arabian Gulf.
The fish is mostly pelagic which means it lives in the open seas, contrary to most sharks which live on or near the bottom (referred to as benthic). Researchers say that the whale shark is highly migratory – it can swim the entire length of the ocean just to get to areas that are rich in food.
Normally, sharks give birth to a few, very large babies, but whale sharks are different in that they give birth to very many small babies (hundreds of them) of an average length of just 45 cm. After internal fertilization, it produces eggs which remain inside the abdomen until they hatch.
Current Population Trend
Surprisingly, whale sharks are not well understood, perhaps because they are highly migratory and very elusive. They are known to move to the central west coast of Australia every spring.
Their numbers are going down especially due to harpoon fisheries targeting concentrations of this slow-moving, docile fish. Consequently, the World Conservation Union has marked the whale shark as vulnerable, meaning that the fish faces a significant risk of extinction in the coming years.
Whale sharks live very long (60-100 years), attain sexual maturity very late (not until 30+ years) which means it can take a long time recover from threats due to their slow reproduction rate. However, the main threat comes from fishing activities of man, especially because their flesh is very valuable in some Asian countries.
There are also reports of a large whale shark fin going for more than 13,000 US dollars. They are also caught for their meat and oil, especially by unregulated fisheries. Habitat loss and coastal development are also thought to threaten their existence.
Whale Shark Conservation
Whale sharks are under legal protection in Australian Commonwealth waters as well as in the Maldives, Philippines, India, Thailand, Honduras, Mexico and the US Atlantic waters.
South Africa and Taiwan are considering granting the whale shark full legal protection. In 2002, it was added in Appendix II of CITES (International Trade in Endangered Species) Convention which means that fishing countries will have to demonstrate that any exports came from a sustainably managed population.
Such countries are also mandated to monitor imports and exports. It is hoped that these efforts will prevent the extinction of the threatened whale shark, the largest fish in the world.