Whale Sharks

“One of the greatest mysteries on Earth and the biggest mystery in the Ocean, very little is known about the species. Perhaps rather sadly, the old saying ‘out of sight, out of mind’ is the reason why the human race has not focused upon nor truly understood, until perhaps recently, the importance of the oceans in the existence and survival of life on Earth.”

—Jonathan R. Green

What do we know about Whale Sharks?

Scientific Classification

Order:  Orectolobiformes  (43 species)
Family:   Rhincodontidae     (Only 1)
Genus:   Rhincodon
Species:   R. typus

Whale sharks are fish, not mammals. They do not come to the surface to breath! The name “whale” refers to their size and their feeding behaviour as whale sharks are one of 3 planktivorous shark species. They are is the world’s largest fish and biggest shark ever to exist; even bigger than the extinct prehistoric megalodon!

They reach up to 18 - 20 meters in length and weigh on average around 18 tons (18,000kg), bigger than the average school bus! The largest recorded whale shark caught in Taiwan in 1987 was measured at 20m; she weighed 34 tonnes.

By Simon J Pierce

Whale sharks are one of 3 planktivorous sharks. They are filter feeders, sucking in huge amounts of water with zooplankton, fish and coral eggs and fish larvae making up the majority of their diet. The largest fish in the ocean feeds on the smallest marine creatures.

They are “ovoviviparous” meaning the young hatch from eggs, as with all fish, but the incubation is internal and the young are born alive.

They can carry over 300 fetuses or young, which makes them by far, the most prolific of all sharks. The largest land animal, the elephant only has one young at a time.

The young whale sharks, called “pups” measure between 40 - 60 cm at birth and weigh only 3 – 5 kg.

The largest of all marine creatures, the blue whale gives birth to a calf that measures around 7m and 2.5 tonnes in weight.

They dive to great depths. The deepest dive being to 1928m in the Yucatan Peninsula, yes that is almost two kilometres down.

Temperatures down there are only just a couple of degrees Celsius above freezing.

They are found in all the oceans of the world between around 40° North and 35° South and prefer subtropical and tropical waters with an average temperature between 22°C and 26°C.

Males have claspers.
Females have NO claspers, only pelvic fins.

In the Galapagos, we find 95%+ females!

What we don’t know about Whale Sharks

Although whale sharks are one the biggest fish in the ocean, and although scientists are making great efforts to study them, they still remain a mysterious species. Their wide ocean use and the different ecology and behaviours by juveniles and adults, females and males, making studying these sharks quite the challenge. 

  • No one has even seen whale sharks reproduce. Some fishermen tales mention having seen whale sharks come ventral side to ventral side in Santa Helena, in the Atlantic. Could this be one of the places for whale shark reproduction?

  • Hard to believe but no one has EVER seen a whale shark give birth. What we know about whale shark reproduction is all from a single whale shark caught in Taiwan in 1995.

  • New technology (especially with genetics) is arising to better predict populations of marine species; thus new population assessments must be carried out in order to understand how whale shark constellations are doing worldwide.

  • Whale sharks have been recorded diving to ~2km. Why they make these sporadic deep dives and if this is the deepest they ever go is still not well understood. Are they diving to cool down? Are they using geomagnetic cues to navigate and using the ocean floor to find their bearing? Are they feeding on the way down or on their way up? Are they going further? Current tagging technology only allows us to track them to that depth, but as technology develops we hope to be able to answer this question with more certainty.

  • Only around 40-50 pups or neonates have ever been found in the wild and generally whale sharks are 3 – 4 m in length before they are spotted in the wild which would make them around 3 – 4 years old. So where are they living until this time? We are trying to find out!

  • Adults are not sighted so frequently in coastal aggregations but moreso in oceanic archipelagos such as the Galapagos Islands, Santa Helena, Azores and more. But where are these adults when they leave the waters of these inhabited oceanic archipelagos where do they spend most of their lives? That is one of the questions of our current research.

  • Estimating whale shark growth and age is still one of the missions that researchers are trying to solve. However, some researchers believe whale sharks can live up to around ~130 years of age. (Perry et al. 2018, Pierce et al. 2021)