The whale shark

The whale shark (Rhincodon typus Smith, 1828) is the world’s largest fish, reaching 15 meters (m) and 18 metric tons (Colman 1997). The head is broad and flattened with a large terminal mouth, miniscule teeth, and large gill slits. The eyes are small and located just behind the mouth on each side of the head. There are three prominent ridges along the back. The first dorsal fin is larger than the second dorsal fin and is set midway back on the shark. Whale sharks have distinctive markings of pale white spots and stripes on their dark dorsal surface, which resembles a checkerboard pattern. It has been suggested that this checkerboard pattern functions as camouflage in the pelagic environment (Wilson and Martin, 2004). Since the arrangement of spots is specific to the individual, photographic identification libraries are being complied for whale shark populations around the world (ECOCEAN).

Habitat and diet

Though Whale Sharks have several hundred teeth, they don’t use them to eat. Instead, these fish are filter feeders, swimming forward to swallow prey. They are carnivorous, eating krill, crab and fish larvae, small schooling fish, and jellyfish. Humans are not on the menu. 

Whale Sharks live in all warm and tropical seas, are migratory, and swim more than 1,000 metres below the surface. Feeding aggregations occur seasonally at several locations, including Ningaloo Reef.

Where do whale sharks live?

What is well known is that whale sharks live in all of the world’s tropical and warm temperate seas and prefer surface water temperatures of 21 to 25 degrees Celsius. They are migratory, with individuals swimming thousands of kilometers to places where food “pulses,” like mass coral spawning events, at the same time every year. You’ll find no couch-potato habits among whale sharks, despite their size.

Whale sharks are considered to be highly migratory. Some moved over 8,000 miles in approximately three years (Eckert and Stewart 2001). In the Caribbean, specimens tagged off Belize moved westward to Honduras and others northward to the Yucatan peninsula (personal communication, R. Graham Wildlife Conservation Society). There are reports of a few sharks that have moved from Meso-American waters (e.g., Belize, Honduras) into the southern Gulf of Mexico (personal communication R. Graham, Wildlife Conservation Society). Two immature male whale sharks tagged off Holbox, Mexico, moved in different directions. One moved south to Honduras and the other moved north to Brownsville, Texas, (personal communication R. Hueter, Mote Marine Laboratory). There is no information on movements of whale sharks from the Caribbean Sea to the northern Gulf of Mexico.

Behaviour and reproduction

Whale Sharks do give birth to live young, but not in the way you’re thinking. The Whale Shark is oviparous, meaning the female sharks produce eggs that are hatched inside of her. These eggs are not all born at once, but are born in a steady stream over a certain period.

Able to birth around 300 young, Whale Sharks reach sexual maturity at 30 years and live to a total of around 70 to 100 years.

Threats

The Whale Shark population is at risk. Vessel strikes and being caught accidentally by commercial fishing vessels has led the Whale Shark to be considered a vulnerable species. 

Some Facts:

  • Whale Sharks can live up to 100 years.
  • Whale Sharks will often “cough” to clear particles from their filter pads.
  • Whale Sharks are covered in a pattern of spots that is unique to each shark, much like human fingerprints.
  • Sometimes, Whale Sharks allow swimmers to grab their fins and catch a ride!
  • A whale shark’s mouth is about 1.5 m wide. Inside, they have rows of over 300 teeth, but they don’t use these teeth to eat because they’re filter feeders.
  • While they are meat-loving carnivores, whale sharks do not attack humans. They are filter feeders and eat krill, crab and fish larvae, small schooling fish and jellyfish.
  • The whale shark is ovoviparous, meaning the female produces eggs that hatch insider her.
  • When the young are fully developed, the female gives birth to around 300 live young.

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