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The Explorer's Guide contains a treasure trove of aquatic science resources developed for use in K-12 classrooms. Back to Explorer's Guide.


Whale Shark Scientific Name: Rhincodon typus
Whale sharks are not only the biggest shark, but the biggest fish in the world. This shark can weigh as much as a large school bus. However, this shark isn’t one of the most ferocious—it doesn’t even chase down its prey.



Region: Philippines


Taxon: Fish


Appearance
The world’s largest living fish, the whale shark, can be up to 60 feet (23.6 m) long and weigh as much 44,000 pounds (20,000 kg) or 20 tons. This big fish is primarily blue and has splotchy white stripes that run along the width of its whole body. It also has rows of white spots between the stripes. The spots become denser as they get closer to the head. The blue of the whale shark fades to white near the ventral or stomach area. Like most sharks, this fish exhibits countershading. This means the shark has a dark-colored back and a light-colored belly. When viewed from below, the whale shark blends in with the brightness of the sunny waters above. Viewed from above, the shark blends in with the dark ocean bottom. Countershading camouflages the animal, allowing it to hide in the open ocean. The whale shark also displays disruptive coloration or a form of camouflage that breaks up the shape of the animal making it harder to be seen. The spots and stripes serve to break-up the outline of this huge fish’s body. From far away, the whale shark may only look like a small school of fish

The whale shark has a huge mouth. In contrast, the eyes are very small. They are located very close to the mouth. The nostrils border the edge of the top of the mouth. Each nostril has a barbel or flaps of skin used in tasting and feeling hanging from it. The barbels are thought to detect how much food is in the water that lies ahead.


Habitat
Whale sharks constantly swim along coast lines, often entering bays and lagoons and circling coral reefs. They may also be found out in the open ocean. This fish is most often found at the surface because that’s where it feeds.

These fish swim alone or in small groups. When waters warm up and corals reproduce, whale sharks gather in large groups of over 100 to feed on the millions of tiny eggs and sperm that are released by the corals. These sharks have even been found swimming with other sharks, dolphins or pilot whales.


Range
Whale sharks live in all the warm and moderately warm parts of all the Oceans.


Diet
Very few sharks are filter feeders like the whale shark. Cruising slowly near the surface with its mouth open, the whale shark feeds on phytoplankton or tiny plants, zooplankton or tiny animals, squid and small fish. They occasionally eat larger fish too. To maintain its enormous weight, the whale shark spends most of its day feeding.

The whale shark doesn’t chew its prey like other sharks; it catches its food with gill rakers or tiny hooks on its gill arches that act like spongy filters. These gill arches strain the water passing through the mouth and collect the food items which are then swallowed.

When there are dense amounts of plankton or tiny plants and animals that float at the mercy of the currents in the water, the whale shark can pump water into its mouth. Moving its head from side to side, the shark opens and closes its mouth up to 28 times per minute. The opening and closing of the mouth and the gill slits at the same time creates a suction, drawing the prey and the water into the shark’s mouth.

These sharks have also been found to position themselves vertically and bob up and down through the middle of schools of fish or thick clouds of plankton. Many smaller fish will swim into the shark’s mouth thinking they are hiding inside a dark cave. Larger fish like tuna often chase after the smaller fish. The whale shark will then move upward so its head breaks through the surface of the water. In doing so, gravity forces all the animals trapped in the shark’s mouth down into its stomach.

Whale sharks have 300 rows of tiny little teeth. These teeth are small because the shark is a filter feeder and doesn’t need sharp teeth to chop up their food.

If the whale shark eats something it doesn’t like, it will force its stomach out of its mouth to get rid of the unwanted item.


Reproduction
In the past, there was much debate among scientists over the means of reproduction of the whale shark. Due to the immeasurable amount of traveling, it has been hard for scientists to study the mating habits. Some scientists believed that whale sharks were viviparous, bearing live pups or babies. Others believes they were ovoviviparous, bearing live pups after they develop inside egg cases or a thin, leathery case that protects each developing pup inside the uterus. However, a whale shark egg case was found in the Gulf of Mexico. This had led scientists to believe the whale shark is indeed ovoviviparous. Through this reproductive method, the eggs remain protected inside egg cases inside the mother’s uterus. Each developing egg is enclosed within an individual egg case. A developing pup feeds off its egg’s yolk. The pups remain inside the egg cases until fully developed and then hatch out. Soon after, the mother gives birth to the pups. The pups are born when they are old enough or large enough to survive on their own. Whale sharks can carry up to 300 pups at a time. Each pup can be up to 2 feet (60 cm) long.


Endangered
>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

Threatened
A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

Vulnerable
A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

Stable
A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

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Threats and Management
Because whale sharks swim long distances all over the world through almost all the oceans, it is hard to track their population numbers. It is also difficult to understand the biology and life history of the fish. We do know that these large sharks are slow to grow and take a long time to reach maturity. These qualities make it hard for whale shark to recover from overfishing.

In the past, many countries have hunted whale sharks for their valuable meat, fins, liver and skin and today some countries still do. Swimming slowly near the surface makes the whale shark an easy target for fishers. The meat is eaten fresh and dried salted like jerky, the liver is processed to make oil, and the fins are used to make soup or used in traditional Chinese medicine.

Countries, like the Philippines, have created laws to protect whale sharks, but often times there is not enough money or people to enforce the laws. Environmental groups, Universities, and local communities have created dive programs for tourists to swim near the whale sharks. This helps to raise awareness and educate people about whale sharks.


Did You Know?
The whale shark is the only living member of its Family, Rhinocodontidae.

Kaiyukan Aquarium in Osaka, Japan was the first aquarium to have a whale shark in captivity. This is their second whale and it is named "Yu-chan". Yu-chan is constantly fed buckets of krill or a type shrimp. In November, the Okinawa Expo Aquarium in Japan just added a new tank to its collection and it holds four whale sharks. This tank is 33 feet (10 m) tall, 120 feet (36 m) long, and 90 feet (27 m) wide.

The sandpapery skin of the whale shark can be up to six inches thick.

Whale sharks won’t hurt swimmers, divers or snorkelers, but they have been known to attack and bump boats. Since it is unlike these gentle sharks to attack, it is believed the whale sharks are taunted, harassed or provoked by the boat’s passengers.


References
Web Sites:
NOTE: The following Web sites are not maintained by the John G. Shedd Aquarium and will open in a new browser window.

Fishbase:
http://www.fishbase.org/Summary/SpeciesSummary.cfm?
ID=2081&genusname=Rhincodon&speciesname=typus


Weight of a school bus: http://www.stnonline.com/stn/operations/schoolbusfaqs/

Kaiyukan Aquarium: http://www.kaiyukan.com/eng/

Okinawa Expo Aquarium: http://www.ocean-park.go.jp/aqua_e/

Print Publications:
Michael, S.W. 1993. Reef Sharks & Rays of the World. A guide to their identification, behavior, and ecology. Petaluma, California: Sea Challengers. 107p. ISBN# 0-930118-18-9.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

Tricas, T.C., Deacon, K., Last, P., McCosker, J.E., Walker, T.I. and Taylor, L. 1997. Sharks & Rays. The Nature Company Guides. McMahons Point, Australia. 288p. ISBN# 0-7835-4940-7.


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Vocabulary Words

Barbels – Flaps of skin near the mouth used in tasting and feeling.


Caudal – Having to do with the end or tail of an animal. The tail fin.


Countershading – A form of camouflage in which an animal has a dark-colored back and a light-colored belly. Using fish as an example, when viewed from below, a fish blends in with the brightness of the sunny waters above. Viewed from above, the animal blends in with the dark ocean bottom. Countershading camouflages the animal, allowing it to sneak up on unsuspecting prey or hide from predators.


Disruptive coloration – A form of camouflage that breaks up the shape of the animal to make it harder to be seen.


Dorsal – The back of an animal. The large fin on the back of a shark; the fin that sticks out of the water when a shark swims near the surface.


Egg case – A leathery protective container that enables shark eggs to mature until hatching.


Extinction – An organism that has not been present on the face of the earth for over 50 years.


Filter feeder – A feeding method in which particles are strained from the water. The animal swims with its mouth open or sucks in water. Gills catch all the food by use of tiny hooks called gill rakers.


Gill arches – The bows or arcs that make up the gills; structures used for breathing that extract oxygen out of water.


Gill rakers – Small hooks on the gill arches that catch and filter particles out of the water passing over the gills.


Krill – A type of shrimp.


Organism – A living thing.


Overfishing – The excessive fishing or catching of aquatic (ocean or freshwater) animals to the point that the amount of animals being caught is greater than the amount of animals born. When more animals are caught than are being born, the aquatic environment is left depleted of the targeted animals.


Ovoviviparous – A form of reproduction in which the young, or in this case pups, develop inside thin leathery egg cases inside the mother. Each pup receives food from a yolk sac inside the egg case. After the pups fully develop, they hatch from their egg cases. Soon after, the mother gives birth to the pups.


Pectoral – The pair of fins that stick out of the side of a fish from behind the gills; used for balance.


Phytoplankton – Microscopic plants that float at the mercy of the ocean currents


Plankton – Plants or animals that float at the mercy of the currents or have weak swimming abilities. For example: phytoplankton, zooplankton or sea jellies.


Pup – A baby shark.


Species – A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.


Traditional Chinese medicine – A form of medicine practiced predominantly in China, Hong Kong, Taiwan, and Singapore. It is based on two counterpart, yin and yang. People get sick when the balance between yin and yang shifts. Natural elements, such as seahorses and other sea creatures, are used to heal disease.


Ventral – The belly of an animal.


Viviparous – A form of reproduction in which the young, or in this case pups, develop inside the mother. Each pup receives food from the mother’s blood through an umbilical cord. The pups are born fully developed and able to hunt and swim on their own. This form of reproduction is referred to as “live birth".


Zooplankton – Microscopic animals that float at the mercy of the ocean currents and have weak swimming ability.


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Whale Shark
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