The largest fish in the sea - friend or foe?

A shark is a fish with really big teeth.
They’ll eat you whole head, hands, and feet.
When there [sic] hungry they’ll track you down.
They’ll sniff you out like a blood- hound.
Adrian C.

I want you to close your eyes. Imagine you are swimming in water of the deepest navy, with empty blue space stretching as far as the eye can see. Beams of light dance down from above. Suddenly a reflection catches your eye and out of the darkness below, a shape starts to materialize. It is a dark grey fish of epic proportions, stretching over 12m in length - that is 12 of you stacked in a line head to toe. As the creature gets closer, you start to make out a beautiful pattern of white spots dusting across its back, like the milky way stretching across the night sky. The large tail fin swishes lazily back and forth. Now you spread your arms wide and they don’t even reach across the width of the shark’s large gaping mouth. Yes, that’s right, you are face to face with a shark possessing a 1m mouth; a dark gaping opening that could easily swallow you whole. But don’t be alarmed, this is not a shark to be scared of; the enormous whale shark feeds solely on plankton, creatures smaller than the length of your little finger, and the odd tiny fish. That might seem like a very large mouth for very small morsels of food, but the whale shark must filter vast quantities of water each day to gain enough food to keep going on its journey through the submarine world. As the water passes through the mouth and out the gills, the plankton is sieved on grating-like gill rakers, and then swallowed, all without the use of any of the shark’s 300 rows of tiny teeth.

The whale shark should not be confused with a whale. It is 100% fish, not a mammal like the humpback whale or the bottlenose dolphin. It is so named because it is the largest fish in the sea, a truly magnificent beast found round the world in tropical or warm temperate (check out the last blog on lobsters to find out the meaning of this word) waters. But it is a very mysterious creature and as a result, little is known about its movements between the odd appearance at certain locations. For example, here on Ningaloo Reef in Western Australia, individuals turn up between March and June each year to partake in a feast as the local oceanic conditions of currents, temperature and nutrients produce a plankton bonanza - it’s like Christmas dinner for whale sharks.

The size of a whale shark is just the beginning of its impressive statistics. Some individuals have been recorded as diving over 1500m down; that’s almost 4 times round your school running track, straight down into the deep! Because these creatures are fish not mammals, they don’t need to return to the surface to breathe, instead they gain all the oxygen they need from the water bathing their gills. Every now and then, however, they are spotted lounging at the surface to feed on swarms of krill or bask like lizards in the sun. Warm and well-fed, they return to the depths, retaining that air of mystery for another day.

What is your favourite food? Ice-cream? Burgers? Cheese and pickle sandwiches? How about watery soup with a gristly shark fin swimming around in it? Sounds pretty disgusting doesn’t it. But in some countries, this dish is a delicacy. Whale shark fins are too big for use in soups but this fish is targeted so its massive fins can be displayed on the walls of restaurants serving shark fin soup. This fishery plus boats hitting and injuring whale sharks in certain areas, has resulted in this species being declared vulnerable to extinction. What does this mean? It means we need to protect and conserve this beautiful creature so that hopefully one day we can watch a 12m whale shark arise from the mysterious deep, together!

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