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Gentle giants of the ocean: 10 fascinating facts about whale sharks – the world’s biggest fish

8 min read

Inspiring People
Source: Unsplash/NOAA

Magnificent and mysterious migratory leviathans of the deep, Whale Sharks are listed as endangered on the International Union for Conservation of Nature’s (IUCN) Red List, but there are things we humans can do and are doing to help.

gentle giants of the ocean: whale sharks up close

Few creatures on the planet inspire such awe and wonder. They are the largest shark species, and the largest fish on earth. These are whale sharks, leviathans of the deep, as mysterious as they are enormous, and they have never harmed a human.

 

These huge creatures can grow up to 12 metres long (about 65 feet), and weigh 75,000 pounds. A whale shark's size rivals that of large whales, but despite their impressive proportions, whale sharks are often referred to as

1. Whale sharks aren’t whales, but the worlds largest fish. These huge creatures can grow up to 12 metres long (about 65 feet), and weigh 75,000 pounds. A whale shark’s size rivals that of large whales, but despite their impressive proportions, whale sharks are often referred to as “gentle giants”. Source: Unsplash/NOAA

Although its mouth can stretch to four feet wide, a whale shark’s teeth are so tiny that they can only eat small shrimp, fish and plankton by using their gill rakers as a suction filter. They feed by gulping mouthfuls of water and forcing that water through their gills. Prey gets trapped in dermal denticles and a rake-like structure called the pharynx. This amazing creature can filter over 6,000 litres/1,500 gallons of water an hour through their gills.
2. Eating is laborious work. Whale sharks are filter feeders and can neither bite nor chew. Although its mouth can stretch to four feet wide, a whale shark’s teeth are so tiny that they can only eat small shrimp, fish and plankton by using their gill rakers as a suction filter. They feed by gulping mouthfuls of water and forcing that water through their gills. Prey gets trapped in dermal denticles and a rake-like structure called the pharynx. This amazing creature can filter over 6,000 litres/1,500 gallons of water an hour through their gills. Source: Unsplash/Sebastian Pena Lambarri
There is still a lot to learn about the life cycle of a whale shark. Here is what we do know. Whale sharks are ovoviviparous—females lay eggs, but they develop inside her body. A study showed that it is possible for whale sharks to have several litters from one mating. Whale shark pups are about 2 feet long when born. Scientists are not sure precisely how long whale sharks live, but based on their large size and their age at first reproduction (around 30 years old for males) it is thought that whale sharks may live at least 100–150 years.
3. Whale sharks can live to be very old. It’s thought that less than 10% of whale sharks born survive to adulthood, but those that do may live a long time. There is still a lot to learn about the life cycle of a whale shark. Here is what we do know. Whale sharks are ovoviviparous—females lay eggs, but they develop inside her body. A study showed that it is possible for whale sharks to have several litters from one mating. Whale shark pups are about 2 feet long when born. Scientists are not sure precisely how long whale sharks live, but based on their large size and their age at first reproduction (around 30 years old for males) it is thought that whale sharks may live at least 100–150 years. Source: Unsplash/Dorothea OLDANI
With the exception of the Mediterranean Sea, whale sharks can be found in all temperate and tropical oceans around the world and migrate thousands of miles to different feeding grounds. But moving is slow going, as they move at speeds of little more than 3 miles per hour.
4. Whale sharks are slow swimmers and migrate a long way. With the exception of the Mediterranean Sea, whale sharks can be found in all temperate and tropical oceans around the world and migrate thousands of miles to different feeding grounds. But moving is slow going, as they move at speeds of little more than 3 miles per hour. Source: Unsplash/Jeremy Bishop

4. Whale sharks are slow swimmers and migrate a long way.

The movement of whale sharks was poorly understood until recent decades, when developments in tagging technology allowed scientists to tag whale sharks and observe their migrations. We know now that whale sharks are capable of undertaking migrations thousands of miles long—one tagged shark traveled 8,000 miles over 37 months. Mexico appears to be a popular spot for the sharks—in 2009, a “swarm” of over 400 whale sharks was seen off Mexico’s Yucatan Peninsula.

Many sharks are accidentally caught in fishing gear, as well as caught deliberately for their fins, which are a delicacy in Asia. Their ocean home is also in danger. From climate change warming the water - affecting both habitats, prey and shark population shifts - to plastic pollution, which could cause entanglement or be ingested, especially by filter feeders.

5. Along with other sharks, they are under threat. Many sharks are accidentally caught in fishing gear, as well as caught deliberately for their fins, which are a delicacy in Asia. Their ocean home is also in danger. From climate change warming the water – affecting both habitats, prey and shark population shifts – to plastic pollution, which could cause entanglement or be ingested, especially by filter feeders. Source: Unsplash/Olga Tsai

Whale sharks, and other elasmobranchs such as skates and rays, are cartilaginous fish. Instead of having a skeleton made of bone, they have a skeleton made of cartilage, a tough, flexible tissue. Since cartilage doesn't preserve as well as bone, much of what we know about early sharks comes from teeth, rather than fossilised bone.
6. Whale Sharks are cartilaginous fish. Whale sharks, and other elasmobranchs such as skates and rays, are cartilaginous fish. Instead of having a skeleton made of bone, they have a skeleton made of cartilage, a tough, flexible tissue. Since cartilage doesn’t preserve as well as bone, much of what we know about early sharks comes from teeth, rather than fossilised bone. Source: Unsplash/Jeremiah Del Mar
Whale shark females are usually larger than males. This is true for most other sharks and also for baleen whales, another type of large sea animal that eats small organisms. How can one tell male and female whale sharks apart? Like other shark species, males have a pair of appendages called claspers that are used to grasp the female and transfer sperm when mating. Females do not have claspers.
7. Female whale sharks are larger than males. Whale shark females are usually larger than males. This is true for most other sharks and also for baleen whales, another type of large sea animal that eats small organisms. How can one tell male and female whale sharks apart? Like other shark species, males have a pair of appendages called claspers that are used to grasp the female and transfer sperm when mating. Females do not have claspers. Source: Unsplash/Jeremy Bishop
Whale sharks have a beautiful coloration pattern, with a bluish-gray to brown back, and a white underside. This is an example of countershading and may be used for camouflage. They also have light vertical and horizontal striping on their sides and back, with white or cream-coloured spots. These also may be used for camouflage. Each whale shark has a unique pattern of spots and stripes, enabling researchers to use photo-identification to study them. By taking photos of whale sharks (similar to the way whales are studied), scientists can catalogue individuals based on their pattern and match subsequent sightings of whale sharks to the catalogue.
8. Whale Sharks Can Be Studied by Identifying Individuals. Whale sharks have a beautiful coloration pattern, with a bluish-gray to brown back, and a white underside. This is an example of countershading and may be used for camouflage. They also have light vertical and horizontal striping on their sides and back, with white or cream-coloured spots. These also may be used for camouflage. Each whale shark has a unique pattern of spots and stripes, enabling researchers to use photo-identification to study them. By taking photos of whale sharks (similar to the way whales are studied), scientists can catalogue individuals based on their pattern and match subsequent sightings of whale sharks to the catalogue. Source: Unsplash/Olga Tsai
Because of their gentle nature, it is possible to swim, snorkel, and dive with whale sharks. Excursions where people can swim with whale sharks have been developed in Mexico, Australia, Honduras, and the Philippines.
9. You can Swim With a Whale Shark. Because of their gentle nature, it is possible to swim, snorkel, and dive with whale sharks. Excursions where people can swim with whale sharks have been developed in Mexico, Australia, Honduras, and the Philippines. Source: Unsplash/Ishan @seefromthesky
The whale shark is listed as endangered on the International Union for Conservation of Nature's (IUCN) Red List. It is still hunted in some areas and its fins can be valuable in the shark finning trade. Since they are slow to grow and reproduce, populations may not recover quickly if this species is overfished.
10. Whale Shark Populations Are Endangered. The whale shark is listed as endangered on the International Union for Conservation of Nature’s (IUCN) Red List. It is still hunted in some areas and its fins can be valuable in the shark finning trade. Since they are slow to grow and reproduce, populations may not recover quickly if this species is overfished. Source: Unsplash/Mike L

How Whale sharks help Maintain the Carbon Cycle in the Ocean

Carbon is a crucial element in the life cycle. It is important not just for the stability of ocean ecosystems but also for the entire universe. And because oceans are the world’s biggest carbon sinks, they play a vital role in the carbon cycle.

But how do sharks help the ecosystem in maintaining the carbon cycle?

Well, seagrass beds and other marine plants absorb and store billions of kilograms of carbon. However, as mentioned before, sea turtles and other herbivores pose a great danger to seagrass. In the absence of sharks, they can decimate entire seagrass meadows.

If these seagrass meadows are destroyed, more carbon is released, severely impacting oceans and making them more acidic. Acidic oceans pose a threat to marine life.

Destruction of seagrass meadows also limits the amount of carbon that oceans can absorb, accelerating global warming. So maintaining a stable carbon cycle is part of what sharks do to the ecosystem.

In addition, big sharks like whale sharks store significantly high amounts of carbon in their bodies. And when they naturally die, they sink to the ocean floor and become food for scavengers. This recycles the carbon.

Sharks also help to recycle carbon in the ocean by consuming the dead matter in the ocean. Therefore, interfering with the whale sharks’ ecosystem disrupts the carbon cycle.

Source: OurEndangeredWorld.com

However, illegal fishing does still occur, meaning campaigning against this trade is essential in ensuring a growing Whale Shark Population. Image: © Sherry Magno/WWF

The shark finning trade is slowly decreasing, which is good news for all shark species. However, illegal fishing does still occur, meaning campaigning against this trade is essential in ensuring a growing Whale Shark Population. Image: © Sherry Magno/WWF Source: Sherry Magno/WWF

What can threaten whale sharks’ population growth and how can you help?

Classed as vulnerable on the IUCN Red List, the Whale Shark is a victim of the shark finning trade whereby overfishing can damage growing populations. As an internationally valued species, there is a high demand for Whale Shark meat, fins and oil which are usually obtained through illegal fisheries. Similarly, unsustainable fisheries often catch Whale Sharks by mistake, killing them in the by-catch process.

Recently, Whale Shark tourism has dramatically increased resulting in high numbers of humans swimming with these graceful creatures in their natural habitat. If done correctly, this can benefit the conservation status of the fish, however several operators see the activity as a profit maker, interrupting the Whale Sharks feeding process to entertain tourists. There have also been cases of boat/propeller injuries within this industry.

HOW CAN WE HELP THE WHALE SHARK? 

Science! The main way we can help the Whale Shark is by using scientists to discover more information regarding their life cycles, habitats and overall behaviour. This information can allow specific conservation plans to be put in place, and allocate areas to be protected. The more we know, the more we can do!

The shark finning trade is slowly decreasing, which is good news for all shark species. However, illegal fishing does still occur, meaning campaigning against this trade is essential in ensuring a growing Whale Shark Population.

If visiting or taking part in a Whale Shark diving activity, make sure the operator is a trusted and sustainable company. Most conservation focused providers make this clear prior to your dive!

Sources: OneKindPlanet | WWF | ThoughtCo | WhaleSharksEndangered | OurEndangeredWorld

If done correctly, this can benefit the conservation status of the fish, however several operators see the activity as a profit maker, interrupting the Whale Sharks feeding process to entertain tourists.

Whale Shark tourism has dramatically increased resulting in high numbers of humans swimming with these graceful creatures in their natural habitat. If done correctly, this can benefit the conservation status of the fish, however several operators see the activity as a profit maker, interrupting the Whale Sharks feeding process to entertain tourists. Source: OurEndangeredWorld

Oil remains can harm all different types of animals including Whale Sharks.
Propellers on passing boats also pose a threat to Whale Sharks because the propellers can injure and cut the Whale Sharks. Oil remains can harm all different types of animals including Whale Sharks. Source: WwhaleSharksEndangered.com
And when they naturally die, they sink to the ocean floor and become food for scavengers. This recycles the carbon.
Big sharks like whale sharks store significantly high amounts of carbon in their bodies. And when they naturally die, they sink to the ocean floor and become food for scavengers. This recycles the carbon. Source: OneKindPlanet.org 

This article was originally posted on Apr 27, 2022.

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