The oceans are vast and full of unexpected surprises at every turn of the seashell. You never know what is hiding in the deep waters, buried under the algae. Among the many fascinating creatures of the ocean is a gentle giant: the huge but harmless whale shark, the largest living fish on land (or rather in the ocean). But this magnificent creature is much more fascinating than you might think.
How to spot a whale shark?
Whale sharks (Rhincodon typus) have a somewhat confusing name. They are not whales but sharks. They are the largest sharks currently alive, measuring up to 20 meters long (about the size of a bus) and weighing up to 20.6 tonnes.
This huge fish is known to roam the tropical seas slowly, migrating each spring to breed and feed. These large sharks are very easy to distinguish and differentiate from other species as they resemble spotted catfish except that they are hundreds of times larger. It’s impossible not to notice one if you come across it (in the ocean or in a photo), but here are some of its defining physical characteristics to make sure what you’re looking at is indeed a whale shark.
This fish has a flattened head, a blunt snout above the mouth, and small eyes. The whale shark has a two-tone pattern of light spots on its dark gray back and its belly is white. The patterns of their spots make each individual unique because no two whale sharks have the same patterns – they are like fingerprints. They also have five large, conspicuous gill slits, two dorsal fins, two long pectoral fins, two pelvic fins, an anal fin, and a large tail. But the whale shark’s most striking feature is undoubtedly its mouth.
A whale shark’s mouth is huge, measuring 1.2m wide. Despite its large mouth and body, the whale shark does not eat or attack humans or other larger creatures. These docile creatures are rather filter feeders and their meals consist mainly of plankton, fish eggs, copepods and coral eggs, but they do not refuse small fish and squid. When these sharks are hungry, they open their mouths wide and passively filter out anything suspended in the water. This is the same mechanism used by baleen whales.
The whale shark still has many rows of teeth, but these are vestigial teeth that play no role in feeding. Instead, feeding is by filtration. Rather than using their teeth, whale sharks use specialized flaps called velums that prevent water from flowing back when the shark closes its mouth, preventing food waste.
A plankton-heavy diet
These monumentally sized creatures are well suited to this diet and possess several physical adaptations that allow them to filter effectively. They can process more than 6,000 liters of water per hour thanks to their gills. In addition, the whale shark is equipped with 20 filter pads that allow it to sift an average of 20.7 kilograms of plankton in a day. The whale shark may feed on small creatures, but it makes up for it in numbers.
Whale sharks are slow-moving pelagic species, which means they spend most of their time on the high seas – and they’re not afraid of deep seas. Studies have shown that they can reach depths of up to 1,928 meters, although they prefer warm waters where there is plenty of plankton. Ironically, the biggest shark has the smallest prey: it feeds on plankton, which it sweeps away with its wide open mouth. In fact, whale sharks love plankton so much that they are a good indicator of the presence of plankton, which says a lot about the health of the oceans.
An endangered species whose preservation must be encouraged
Like many other sharks, whale sharks are endangered, both directly and indirectly. With climate change, the waters are becoming increasingly warm and hostile to ocean species. Also, expanding human activity means that creatures like whale sharks have smaller habitats and are often accidentally (or intentionally) trapped in nets.
In southern China and Oman, whale sharks are hunted in large numbers because their fins and oil are considered delicacies. Although they are considered vulnerable species, they are still continuously targeted in several parts of the world, especially in East Asia. These activities, along with the impact of fishing and the pollution of ocean waters, have contributed to the steady decline of their population.
Whale sharks are dying faster than they can reproduce and their population has dropped by 65%, putting them in the ‘endangered’ category of the IUCN red list et alAppendix II of CITES and CMS (Appendix II lists species that are not necessarily threatened with extinction but could become so if trade is not tightly controlled). In short, whale sharks are in trouble and their numbers continue to decline.
Over the years, whale sharks have become popular with snorkelers due to their size and tame nature. That is why swimming with them has long been a tourist attraction. Unfortunately, where there are humans, there are disturbances. Irresponsible tourism has been a threat to their people, as in most cases they are injured by boat propellers. Also, as people want the sharks closer to their boat, they hand-feed them shrimp and small fish, thus interrupting their natural feeding habits.
Conservation efforts from different organizations (WWF, Oceana, etc.) are now being mobilized to help rebuild whale shark populations. In fact, every August 30, Whale Shark Day is celebrated to shine a light on these graceful giants to raise awareness and encourage participation in their conservation.
Whale sharks have a relatively long lifespan. However, few of them make it to adulthood and the threats to them are many and varied. Without serious and rapid conservation action, their numbers are likely to continue to decline.
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