Long live whale sharks!
The predicate of the world’s largest fish falls on the whale shark (Rhincodon typus) with an average length of 5.5 to 10 meters yet still can grow more in length. The largest accurately measured whale shark was 18.8 meters. Its weight can also reach more than 18 tons. However, its large size makes the movement of this fish tend to be slow. Despite their name, whale shark is in no way related to whales. While it does cause many people confusion, the name comes from the fact that it is filter feeders, just like whales. Unlike most sharks, this one incredible fish is docile and pose no real threats to humans. In fact, it gets the nickname the gentle giant and has a naturally calm demeanour, which is popular with eco-tourists that want to snorkel beside it. Swimming with whale shark is a life-changing experience, but it must be done responsibly.
The whale shark belongs to a group called Chondrichthyes, which includes other sea life like sharks, skates, and rays. The criteria of Chondrichthyes are that they have a skeleton made up of cartilage, rather than bone. Whale shark has a wide, flattened head with a mouth that can open to 1.5 meters wide. The first five pairs of gills and dorsal fins in whale shark is also relatively large. In addition, whale shark also has a unique kind of “whisker” growing at the end of its snout. This whisker-like is a sensor organ that functions to detect the movement of prey in the water. Whale shark has a greyish body colour and white spots. The character of the body makes this species quite easy to recognize. In addition, the pattern of white spots on the whale shark is distinctive because it is separate them from others. The difference in the pattern of white spots is used as a tool for identification and the basis for calculating the number of species in a water area by researchers.
Whale Shark habitats are found in the waters of more than 100 countries, most broadly range from tropical to subtropical waters. This massive creature prefers to live in warm ocean waters with temperatures between 21 – 25°C (69 – 77°F), although some are also found in waters with cooler temperatures. Whale shark is completely pelagic (has an open water habitat) and is commonly found offshore and close to land, in lagoons and coral atolls, and near mouths of estuaries or rivers to forage. It often congregates in areas it can feed, which is sometimes makes for a very long migration. A whale shark has been studied to cover a distance of 8,000 miles or about 12,800 kilometres for 37 months. Familiar places you can visit this shark species are Mexico, Belize, Malaysia, Thailand, the Philippines, Japan, Australia, the Galapagos, South Africa, Mozambique, Honduras, Seychelles, and India.
It has long been suspected that whale shark has a long lifespan, and now this has been confirmed using a carbon-dating technique. It turns out this enormous animal can live for at least 50 years and probably far longer. However, whale shark is characteristically slow in growth as well as in sexual maturity, making them relatively few of reproduction. They do not become sexually mature until they are 30 years. The best way to tell the difference between a male and female whale shark is that the males have two claspers near their pelvic fin. The females can have up to 300 shark pups at one time. The whale shark belongs to the order Orectolobiformes (Carpet Shark) and is the only species in the family Rhincodontidae. It is not closely related to other species in the order Orectolobiformes. However, this species has some body characteristics that are like other carpet sharks such as the Nurse Shark and the Zebra Shark. For example, all carpet sharks have two dorsal fins and a mouth located on the front of their body, just in front of the eyes. Whale Shark also has nostrils that are similar to the nostrils of the Leatherback Shark, and the horizontal stripes on the whale Shark’s body are similar to those of the Seahorse Shark. These lines serve as the whale shark’s senses to determine the physical condition of the waters.
A whale shark can have up to 3000 teeth at once and between 300 and 350 rows of teeth. Despite their generous size, the whale shark’s diet is small. It has a main diet in the form of planktonic organisms that float in the waters and are very small in size, such as euphausiids, copepods, and eggs or larvae of fish and squid. Apart from sieving plankton through their gills for much of their nourishment, whale shark is also occasionally seen sieving small fish, such as sardines and anchovies and cuttlefish or squid. In general, whale shark hunts for prey in three diverse ways, namely: Swimming while filtering water (subsurface passive feeding): whale sharks swim with their mouths open while sieving water-borne prey through the gills. Swim while sucking water (surface ram filter feeding): whale sharks swim while sucking water and eat prey stuck in the gills. Standing vertically while sucking water (stationary/vertical suction feeding): whale sharks stay in place vertically while opening and closing their mouths to suck water with their mouths and gills, so that all prey will be filtered out. Feeding in this way allows the whale shark to sieve prey that is actively moving, such as small fish, which generally escape passive feeding techniques. The World Wildlife Fund says that a whale shark can process more than 6,000 litters of water in an hour with their gills.
In 1999, whale sharks were included in appendix II of the Convention on Migratory Species (CMS), which means that whale sharks will only ‘feel’ a significant impact if their protection and management is implemented through international cooperation. This shows that conservation efforts for these species need to be carried out through networks between various countries. In 2000, the whale shark was included in the red list for threatened species by the International Union for Conservation of Nature (IUCN) with a vulnerable status, which means that its population is estimated to have decreased by 20-50% within 10 years or three generations. Then in 2002, whale sharks were finally included in appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which means that international trade for this commodity must go through rules that ensure its use will not threaten its sustainability in nature. In 2016, the whale Shark was listed on the International Union for Conservation of Nature (IUCN) Red List for Endangered Species with an endangered status. The status is one level higher than before, in 2000 (Vulnerable).
Due to their size, whale sharks have very few, if any natural predators and threats in the wild, but problems begin to occur for them when humans get involved. Whale sharks are highly valued on international black markets for their meat, fins, and oil, and this means that they are becoming a species targeted by poachers. It is also thought that the most significant threat to whale sharks is habitat loss or degradation in the form of overfishing of reef fish, coastal development, land-based pollution, increased boat traffic and noise pollution. What is gathered from data that is available, the whale shark is at risk of becoming extinct, and we would possibly lose one of the world’s most gentle giants. Hence, more whale shark conservation efforts are desperately needed.