Everyone loves a gentle giant, but how much do you know about
the world's largest fish?! Dive in below to learn more and see how you can help this endangered shark species.
FAMILY: Rhincodontidae
SCIENTIFIC NAME: Rhincodon typus
COMMON NAME: Whale Shark
TYPE: Fish
The name 'whale shark' comes from their size and not from being a part of the marine mammal family- even though some people are tricked into thinking so. Whale sharks are sharks as well as the biggest (known) fish!
IUCN Red List Status: Endangered (assessed 2016)
SIZE:
Whale sharks can reach a believed max length about 65ft (20m) although most specimens observed are 19.7-39.4ft (6 -12m) in length. Additionally, as is the case with many other sharks, female whale sharks tend to be larger than males.
AVERAGE LIFE SPAN:
It is estimated that whale sharks live 60 years on average but may live upwards of 150 years!
Despite their large size, these animals are hard to track making many aspects of these migratory sharks unexplained and still lots to discover about their life patterns and behaviors. Scientists believe both male and female sharks reach sexual maturity around 29.5ft (9m) with their maximum life expectancy still unknown.
It's generally accepted that whale sharks are ovoviviparous (aplacental viviparity), a method of reproduction in which eggs develop inside the female’s body hatch internally. Whale shark females can give birth to hundreds of pups at a time, each measuring around 20in in length.
These sharks are known to migrate following seasonal feeding events and utilize breeding areas, although specifics of breeding and birth are still unknown. However, there's evidence that the waters off Taiwan and areas around the Philippines may be important birthing areas during the summer months.
DISTRIBUTION:
Whale sharks are highly mobile with daily movement rates of 24–28 km based on data from tethered geo-positioning tags. Sightings have been reported in about 124 countries. Now that's one full passport!
Their migrational movements are attributed by some researchers to timing of plankton blooms or changes in water temperature. They are primarily solitary animals, but on rare occasions are observed in aggregations of 100 or more individuals although the exact reasons why are not well understood.
Whale Sharks spend the majority of time close to the surface, but dive to at least 1,928 m in depth. They occur in warm, tropical waters globally most commonly in oceanic and coastal waters (with the exception of the Mediterranean Sea). They're often seen offshore but sometimes coming close to inshore areas like lagoons or coral atolls.
DID YOU KNOW:
Genetic results indicate that two major subpopulations of whale sharks exist! A population in the Atlantic Ocean and another in the Indo-Pacific, respectively.
Watch more on the NAT GEO channel
DIET:
One of three species of filter feeding sharks, whale sharks feed on tiny floating plankton, fish and coral eggs and zooplankton that they filter from the water column. These sharks will also eat sea jellies, small crustaceans, squid, and small fishes like anchovies, sardines or mackerel that are caught.
Whale sharks are known to aggregate at the surface to exploit seasonal events like fish spawning & zooplankton blooms. In fact, scientists believe that some individuals swim across entire oceans to arrive just in time for such occasions.
While feeding, whale sharks move their heads from side to side, using their large mouths and specially designed 'teeth' like a vacuum to collect morsels from the seawater as they glide slowly by, moving no faster than 3mph (5kph).
These slow moving behemoths tend to spend most of the daytime in shallow depths feeding, sometimes right at the surface and are often sighted in groups.
During night hours and if they are swimming over greater distances, researches note they tend to dive deeper, where they're recorded at reaching depths of 3215ft (980m)- the maximum the instrumentation used could measure!
DID YOU KNOW:
Whale sharks are covered with unique white spotted patterns that vary individual to individual - like human fingerprints. Whale shark researchers utilize specialized computer software to identify individuals from photos and use their spot patterns to help track their movements.
CONSERVATION:
Humans pose the greatest threat to the already endangered and largely depleted whale shark population.
Besides climate change which impacts the entire planet being a continuous threat, whale shark meat is seen in some countries as a delicacy as well as being impacted by the shark fin industry inwhich their large fins can sell at very high prices. Actually their hides, livers and cartilaginous skeleton all add up to a very high values per animal taken which makes them a target of illegal fishing and permitted commercial operations alike.
It's true that many of the larger commercial fisheries for Whale Sharks have now ceased, according to IUCN data, the active fishery in Chinese waters is almost certainly unsustainable and is likely the largest single direct threat to Whale Shark recovery in the Indo-Pacific region.
While they are protected in a number of countries as a focal species for marine tourism industry, whale sharks are frequently fished illegally because of poor or non-existent enforcement of existing regulations. If that isn't enough pressure, these sharks are often victims of bycatch, entanglement in discarded netting and often being victims of boat strikes.
With the increase of oceanic shipping lanes and expansions in oceanic drilling/fossil fuel industry activity in areas close to known feeding areas, there's a serious risk of vessel strikes since these sharks routinely feed close to surface where propeller injuries are unfortunately common.
Additionally, since whale sharks typically sink upon death means that ships may not register or report strikes which contribute to incidents unlikely being documented making tracking their population even harder for researchers.
And while eco-tourism may being doing some good in the fight to help save sharks and spurring conversation around marine protected areas the industry poses an indirect threat to whale sharks and marine ecosystems in general.
"Inappropriate tourism" like incidents of interference/harassment, crowding or provisioning in addition to pollution, over-development/habitat destruction for resorts or other attractions close to marine ' hotspots' may do more harm than good when they result in displacement from preferred habitats for wildlife.
The need for better enforcement of existing laws and establishing better regulations worldwide for Whale Shark protection is crucial to their survival. More education and awareness programs for fishers, tourists, wildlife management, local governments, etc. are also vital for a more stable future for threatened animals and marine habitat.
Check out more in-depth information at these source links!