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

October 1
Yosemite National Park Created (1890)
October 2
San Diego Zoo Founded (1916)
October 3
James Herriot, English Veterinarian, Born (1916)
October 4
Feast Day of St. Francis of Assisi, Patron Saint of Ecology
October 5
Catherine Cooper Hopley, British Herpetologist, Born (1817)
October 6
Mad Hatter’s Day
October 7
Henry A. Wallace, Secretary of Agriculture, Born (1888)
October 8
World Octopus Day
October 9
Vajont Dam Disaster (1963)
October 10
Dnieper Dam Began Operation (1932)
October 11
Big Cypress and Big Thicket National Preserves Created (1974)
October 12
William Laurance, Tropical Conservationist, Born (1957)
October 13
International Day for Disaster Risk Reduction
October 14
Timpanogos Cave National Monument Created (1922)
October 15
Isabella Bird, Pioneering Eco-traveler, Born (1831)
October 16
World Food Day
October 17
Oliver Rackham born (1939)
October 18
Clean Water Act established (1972)
October 19
Research Vessel Albatross Launched (1882)
October 20
OPEC Oil Embargo (1973)
October 21
“Ding” Darling born (1876)
October 22
Wombat Day
October 23
Cumberland Island National Seashore established (1972)
October 24
Antoni von Leeuwenhoek born (1632)
October 25
Secretary of the Interior Convicted in Teapot Dome Scandal (1929)
October 26
Erie Canal Opens (1825)
October 27
Golden Gate and Gateway National Recreation Areas Created (1972)
October 28
Henry Mosby, Wild Turkey Biologist, Born (1913)
October 28
First Ticker-tape Parade Held (1886)
October 29
Stanley Park, Vancouver, Dedicated (1889)
October 30
UNESCO Designates 9 Natural World Heritage Sites (1981)
October 31
Lincoln Highway Dedicated (1913)
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