International Whale Shark Day

Anglers are known to exaggerate the size of the fish they catch, but today we’re covering a fish whose size doesn’t need any help.  The whale shark is the world’s biggest fish, and August 30 is its own day.  Happy Whale Shark Day!

Whale Shark (photo by Elias Levy)

So, first off, let’s be clear—this animal is not a whale, but it is a shark.  That makes it a fish, not a mammal, and it is clearly the world’s biggest fish (in second place is the basking shark, barely half the size of the whale shark).  Mature whale sharks are the size of a school bus, as long as 50 feet and as heavy as 40 tons.  Big monsters, eh?

But, no, they aren’t monsters.  Whale sharks are gentle creatures—big to be sure, but docile to the extreme.  They live in tropic seas around the globe and generally inhabit shallow water and swim near the surface, frequently encountering humans.  A tourist industry has grown around seeing and swimming with whale sharks, which often enjoy a little scratch behind the, uh, gill slits.

Whale sharks are ancient creatures, based on the fossil record, but have been known as living specimens for only two centuries.  Females give birth to live young, dozens at a time.  Various descriptions state that the animals “migrate,” but it seems to me that a better description is that they swim continuously, often covering long distances.  Their lifespan mimics their physical size—up to 70 years. They filter small animals out of the water column, just like the baleen whales (and hence their name), eating as much as 50 pounds per day.  But unlike filter-feeding whales, whale sharks also can pump water actively through their gills, causing a suctioning effect to capture small fish and other organisms.

Whale shark showing pattern of light dots and shapes (photo by Nicholas Lindell Reynolds)

Individual whale sharks are covered with light colored markings, mostly round,  in patterns that remain constant over time and allow individuals to be identified.  A catalogue of more than 7,000 individuals has been created, but overall population size is much larger, perhaps 100,000 or more, according to IUCN. 

However, IUCN also estimates that whale sharks have decreased in abundance from pre-exploitation levels.  Populations in the Indo-Pacific are down about two-thirds, and in the Atlantic about one-quarter.  Because the species likes shallow water and does not avoid humans, overfishing and vessel strikes have caused the population decline.  Therefore the species is judged as “endangered” by IUCN and classified as an Appendix II protected species by CITES.

I’ve looked extensively to find the origin of International Whale Shark Day, but with no luck.  The day, it seems, is much like the animal it honors—silent and mysterious.  Tired of the cliched expression “the elephant in the room”?  I recommend trying “the whale shark in the aquarium!” 

Whale sharks and human swimmers are compatible (photo by Feefional123)

References:

Australian Department of Agriculture, Water and the Environment.  Whale Shark (Rhincodon typus).  Available at:  https://www.environment.gov.au/marine/marine-species/sharks/whale-shark.

Pierce, S. J. and B. Norman.  2016.  Rhincodon typus.  The IUCN Red List of Threathened Species.  Available at:  https://www.iucnredlist.org/species/19488/2365291#text-fields.

World Wildlife Fund.  Whale Shark.  Available at:  https://www.worldwildlife.org/species/whale-shark.  

This Month in Conservation

November 1
Ansel Adams Shoots “Moonrise” (1941)
November 2
National Bison Day
November 3
William Cullen Bryant Born (1794)
November 3
Rosalie Edge, Conservationist and Suffragette, born (1877)
November 4
UNESCO Created (1946)
November 5
Ethelwynn Trewavas Born (1900)
November 6
International Day to Protect the Environment during War
November 7
Costa Rica Constitution Enacted (1949)
November 8
World Town Planning Day
November 9
First Live Panda Leaves China (1936)
November 10
Guinness Book of World Records Born (1951)
November 11
Leonardo DiCaprio Born (1974)
November 12
Salim Ali Born (1896)
November 13
Amory Lovins Born (1947)
November 14
US Crushes Elephant Ivory (2013)
November 15
America Recycles Day
November 16
Global Climate Change Research Act Passed (1990)
November 17
David Livingstone Arrives at Victoria Falls (1855)
November 18
Asa Gray, Father of American Botany, Born (1810)
November 19
World Toilet Day
November 20
John Merle Coulter, Pioneering Botanist, Born (1851)
November 21
Lava Beds National Monument Created (1925)
November 22
Grofe’s “Grand Canyon Suite” Premiered (1931)
November 23
National Eat-A-Cranberry Day
November 24
“On the Origin of Species” Published (1859)
November 25
Nikolai Vavilov, Pioneering Russian Agronomist, Born (1887)
November 26
Anna Maurizio, Swiss Bee Expert, Born (1900)
November 27
Bill Nye, the Science Guy, Born (1955)
November 28
Elsie Quarterman, Plant Ecologist, Born (1910)
November 29
U.S. Rations Coffee (1942)
November 30
Mark Twain, American Humorist, Born (1835)
January February March April May June July August September October November December