Size: the whale shark holds the remarkable title of being the largest fish on the planet. In fact, it is the largest known fish to have ever lived. Due to its immense size and cartilaginous skeleton, accurately measuring the weight of a live whale shark is a challenging task. The largest documented measurement of a whale shark reached an astonishing 61.7 feet (18.8 m) in length. On average, these magnificent creatures measure between 18 and 32 feet (5.5-9.8 m). Even at birth, whale sharks are not to be underestimated, with newborns measuring between 21 and 25 inches (53-64 cm) long.
Body Composition: whale sharks possess a distinct anatomy, characterized by a broad, flat head, relatively small eyes, and five large gill slits. They feature two dorsal fins, two long pectoral fins, two pelvic fins, and one anal fin, all of which contribute to their graceful movement in the water. Notably, the whale shark has a unique evolutionary remnant called a vestigial spiracle, located behind its eye. This spiracle is a relic of its common ancestry with bottom-dwelling carpet sharks.
Unlike most shark species, the whale shark's mouth is positioned at the front of its head, rather than on the underside of the rostrum. This terminal mouth adaptation allows for efficient feeding. Speaking of feeding, the whale shark boasts an enormous mouth that can extend up to an impressive 4 feet (1.2 m) in width. Within its mouth, specialized flaps called velums play a crucial role in preventing food loss by stopping the backflow of water as the whale shark closes its mouth.
Furthermore, the skin of an adult whale shark is as thick as 4 inches (10 cm) and possesses a rubber-like consistency, providing it with protection against potential predators. Among the few creatures that pose a threat to these gentle giants are killer whales, great white sharks, tiger sharks, and unfortunately, humans.
Color and Teeth
Whale sharks exhibit a captivating two-toned pattern on their dark gray back, adorned with light spots, while their undersides are white. Remarkably, each whale shark boasts its own individual spot pattern, much like human fingerprints, making them truly unique. As for their teeth, they are small and point backward, seemingly serving no significant role in feeding. Along the inner surface of each jaw, there are approximately 300 rows of these tiny teeth, positioned just inside the mouth.
Diet: the whale shark sustains itself primarily on a diet of zooplankton, including sergestid shrimps, fish eggs, krill, jellies, copepods, coral spawn, and small fishes such as sardines and anchovies. Due to its narrow throat, comparable in size to a quarter, the whale shark can only consume small prey. Despite its enormous size, it relies on tiny organisms to satisfy its nutritional needs.
Feeding Behaviors: the whale shark employs a fascinating feeding mechanism known as "cross-flow filtration." This intricate process enables the shark to filter food particles from the water without obstruction. As water passes through the gills, particles with more momentum continue toward the back of the mouth in a concentrated stream. Consequently, a bolus or spinning ball of food forms in the throat, eventually triggering a swallowing reflex.
Whale sharks exhibit various feeding methods depending on the concentration of food in their surroundings. When food concentrations are high, they utilize either active suction feeding or vertical suction feeding. Active surface suction feeding is the most common method, characterized by the shark swimming in a normal orientation while feeding. In contrast, vertical suction feeding occurs when food is densely concentrated, with the shark remaining stationary in a semi-vertical position facing the surface.
During both active surface and vertical suction feeding, the whale shark opens and closes its massive mouth, creating a strong suction force that allows it to consume substantial volumes of water and prey. It's worth noting that during feeding sessions in environments like the Ocean Voyager, whale sharks employ this suction-type feeding style, following feeding ladles along the water's surface. In the case of active surface feeding, the top jaw typically breaks the water's surface.
Range: whale sharks are found across the globe in tropical Atlantic, Pacific, and Indian Oceans. They typically inhabit regions between approximately 30 degrees North and 35 degrees South, but sightings have been documented as far as 41 degrees North and 36.5 degrees South. These vast ranges underline the widespread distribution of these magnificent creatures.
Habitat: while whale sharks are primarily offshore dwellers, they occasionally venture close to shore, often entering lagoons or coral atolls. They frequently frequent shallow water areas near bays and coastal regions where upwelling occurs, especially during seasonal plankton blooms. These areas provide an abundance of food, crucial for the whale shark's survival.
Whale sharks follow an ovoviviparous reproductive strategy, in which the embryo develops within an egg inside the mother's uterus. When the time comes, the young are fully formed and released into the sea. It is interesting to note that a documented litter size of over 300 pups is the highest on record, shedding light on the reproductive potential of these remarkable creatures.
Unfortunately, very little is known about whale shark mating behavior. Observations in their natural habitat have been extremely rare, with only two instances recorded to date. Consequently, no observations of whale shark mating have taken place in an aquarium setting.
The conservation status of the whale shark is a matter of grave concern. Currently classified as "Endangered" on the IUCN Red List, these incredible creatures face numerous threats to their survival. Their plight is recognized through their inclusion in Appendix II of both CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) and CMS (Convention on the Conservation of Migratory Species of Wild Animals).
Whale sharks are particularly vulnerable to entanglement in fishing nets, collisions with boats, ingestion of marine debris and microplastics, and, regrettably, human interference resulting from unregulated tourism. In regions like southern China and Oman, opportunistic fishing practices further contribute to the threats faced by whale sharks.