It is the largest fish in the world; it has hundreds of small teeth that it does not use, its body is covered with polka dots to form the so-called “chessboard,” and during the day, it prefers to swim on the surface. Still trying to figure out who we are talking about? Okay, here it is: it’s the Whale Shark!
To celebrate International Whale Shark Day on August 30, the World Sustainability Foundation and Friend of the Sea® will take you into the world of the Whale Shark, the only species in the genus Rhincodon and family Rhincodontidae.
This species is red-listed by the International Union for Conservation of Nature (IUCN) as endangered. The main causes of risk to the whale shark stem from humans: bycatch, ship collisions, and pollution. That is also why the World Sustainability Foundation supports various projects and campaigns to protect sharks.
For example, it supports the conservation efforts of the Maldives Whale Shark Research program. Also, it launched a fundraising campaign on Change.org to push home delivery companies, such as Just Eat, Deliveroo and Menulog, to remove shark fin soups from their menus.
You can visit the Save the Sharks Campaign page to look at the initiatives taken by the WSF and Friend of the Sea® over the years. While to learn more about the Whale Shark, where you can spot this animal that is harmless to humans, and why it is also called a “carpet shark,” continue reading.
International Whale Shark Day to all!
The Whale Shark is the only specie of the genus Rhincodon and the only extant member of the family Rhincodontidae. The look is typical of the shark, however it has a wider body and flattened on the back, with a wide and flat head. Whale Shark mouth is big and, unlike other sharks, mouth is located at the front of the head rather than on the underside of the head, to best fulfil the plankton filtering function.
The body is grey-green, covered by a variety of white spots (also called ‘’ chessboard’’).
Despite their large size and ability to swim long distances for many hours, they move at low speeds compared to other species. They spend the day near the surface and swim to greater depths at night. Both day and night, and temperature changes, have an effect on the routes of the Whale Shark.
NUTRITION
The Whale Shark is a filter-feeding ‘’carpet shark’’, which moves slowly. In fact, is one of the only 3 species of shark to feed filtering the water rather than actively hunting their preys. To do this, it implements 2 different strategies: like the other two filter-feeding sharks (basking shark and megamouth shark) the Whale Shark can perform the so called ‘’passive filtering’’, just swimming with the mouth wide open to capture as much plankton as possible. Otherwise, the Whale Shark can actively filter the water (is the only shark who can do that), remaining motionless and sucking water for suction. This system is implemented on the surface, when the Whale Shark is in presence of an high concentration of plankton. This animal doesn’t feed only on plankton, but also on: krill, crab, jellyfish, squid, anchovies, mackerel, tuna, sardine.
Through a particular branchial structure traps planktonic organisms and then swallows them in the esophagus with movements of the head (called ‘’hiccup’’) that optimize the swallowing of food, or it also sucks small fish to swallow them directly into the stomach. Although they have hundreds of small teeth, these do not have any function in feeding and are therefore ‘’vestigial’’, that’s what remains of an ancient past as an active predator. Food is instead retained by special filter pads, which are a modification of the fifth pair of gill slits.
REPRODUCTION
The Whale Shark is ovoviviparous (which means that reproduction takes place through internal fertilization) and the female gives birth to live cubs, usually one or two, about 50 or 60 cm large. Sexual maturity is reached very late, it is estimated at about 30 years old. So reproductive rates are very low if we consider them in relation to what happens for most fish: the Whale Shark doesn’t reproduce annually, but tends to reproduce every 3 years.
WHERE DOES THE WHALE SHARK LIVE?
The Whale Shark is a migratory animal, which lives in the tropical and temperate-warm waters of the entire globe. In particular, it can be found off the Seychelles, Mauritius, Zanzibar, Madagascar, Mozambique, Natal and Maldives. In the Pacific Ocean it runs the Kuroshio current, in the Gulf of Mexico and in the Caribbean area it often passes near Costa Rica, but the main area for observation is Ningaloo Reef, in western Australia. The largest gathering point in the world is in the area of Playa del Carmen, Isla Mujeres and Holbox, in Mexico.
CONDITION AND MAIN THREATS
Currently Rhincodon typus is classified as endangered for the IUCN red list of threatened species. Human activities are certainly the most harmful for this species, including: trapping in fishing nets, ship collisions, directed fishery and habitat pollution. In fact, the Whale Shark often spends its time close to the surface, and for that is one of the most species at risk of ship collision. Unfortunately, there’s no sign of these incidents because if a Whale Shark is hit by a ship’s hull, most of the time it has no escape and ends up in the depths of the sea. So, today the experts were able to trace the dynamics of the incidents through the satellite ‘’Global Shark Project’’: in this way 350 specimens were followed, equipped with electronic tags, thus mapping their position and discovering that they were often along the routes of large ships (some data show that 92% of the horizontal space occupied by sharks overlaps with the one of the
large fleets’ activities). Another threat is surely intensive fishing: in fact, Whale Shark is considered an important food source in many local cultures (for its meat, the trade of fins, the extraction of liver oil and its use in traditional Chinese medicine). Do not underestimate the pollution, as it has been estimated that a Whale Shark can ingest up to 137 pieces of plastic per hour!
This has led many international biodiversity protection organizations to include this specie in protection schemes for the safeguarding of endangered wildlife. For example, CITES (Convention on International Trade in Endangered Species) has incorporated the Whale Shark into the convention to regulate its fishing and international trade.
5 FUN FACTS ABOUT WHALE SHARK:
- Did you know that it is the largest fish in the world? In fact, it can reach the length of 12 meters (or a little more) and weigh over 8 tons!
- The name ‘’Whale Shark’’ refers to the size of the fish, being as large as some species of whales, in addition to its filtering habits that are not far from those of Mysticeti (a suborder of Cetacea consisting of the whale bones, like Humpback whale, Rorquals, Pygmy right whale, Grey whale and Right whales);
- It’s a quiet animal, not dangerous for man;
- Life expectancy goes over 60 years of age and is expected to reach up to 100 years or more!
- Very interesting is that each specimen has a unique pattern on its skin: in fact, each one has its own precise ‘’chessboard’’, a kind of unique and unrepeatable fingerprint.
