October 15 – A Descent into the Maelström

Today’s factismal: Basking shark corpses are sometimes mistaken for sea monsters.

Have you ever seen a sea monster? If you’ve seen a basking shark, then you have. The basking shark or Cetorhinus maximus (that’s “big critter with a sea monster nose” in science-speak) is one of the world’s largest fish; at 40 ft long and 40 tons, it outweighs every other fish but its near relative, the whale shark. And much like its cousin, the basking shark is a filter feeder that swims about looking for tasty, tasty plankton to nibble on.

A basking shark hunting for plankton (Image courtesy New England Basking Shark & Ocean Sunfish Project)

A basking shark hunting for plankton
(Image courtesy New England Basking Shark & Ocean Sunfish Project)

These amazing sharks are seen everywhere from the Bay of Fundy in Canada to the Florida shores. They are known to pine for the fjords of Finland and to cavort in the Mediterranean as they swim down to the Ivory Coast. They are also seen from Argentina to South America, and from Australia to Chile. Basking sharks have been sighted in the California surf and the Alaskan ice, and are popular visitors to Hawai’i. In short, these guys get around! And no wonder – when you are as long as a bus and weigh as much as three full-grown elephants, you have to keep on the move just to find enough food to eat. Some scientists estimate that a basking shark will spend 10 to 15 hours a day looking for the microscopic plankton that is its primary food source.

The basking shark is born alive from an egg that hatches in its mother’s oviduct; they then spend a few months maturing before being born again into the salty ocean water. Since they have no placentas, during the last part of their maturation the baby sharks eat their mother’s eggs to survive! (That’s oophagy to all true shark nerds.) After being born, the baby basking shark is a cute and cuddly little four foot long bundle of joy. It immediately begins to hunt for plankton and sets about growing large enough to make more baby basking sharks, a feat which takes about six years to accomplish. Every couple of years thereafter, the females will bear more young while the males look for a good paternity test. After about fifty years, the basking shark dies of old age – and that’s when the weirdness begins.

Three images of basking sharks (Image courtesy New England Basking Shark & Ocean Sunfish Project)

Three images of basking sharks
(Image courtesy New England Basking Shark & Ocean Sunfish Project)

Because basking sharks are sharks, their corpses can float. And those corpses are usually scavenged of the gooshier bits first: the head, the belly, and the fins. That leaves behind a long, sinuous spinal column with a bulb on one end where the head used to be and a ratty tail where the tail used to be and little flaps where the fins used to be. Squint at it in the right light, and the thirty-foot long “globster” looks more than a little like a sea monster. And that’s how they’ve been reported in cases such as the Zuiyo Maru “plesiosaur” (warning: gory!).

Perhaps it was this sea monster-like appearance that caused the Canadian government ot put a bounty on the basking shark from 1945 to 1970. Or maybe it was the mistaken idea that they would eat all of the fish. But, whatever the reason, the basking shark was hunted nearly to extinction and is only now starting to recover. Which makes a sighting of one a rare occurrence and of great scientific interest. If you happen to see one, then please head over to the New England Basking Shark & Ocean Sunfish Project and let them know!

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