Cerulean Colossus

A little introduction to the world's biggest fish

- Text by Katie Brooks

The whale shark, Rhincodon typus, is a slow-moving filter feeding shark and the largest extant fish species The whale shark is perhaps one of the great mysteries of our ocean; the biggest fish in the sea and yet it was not described by science until 1828. Though estimated to have existed for over 60 million years, however, only a meagre 320 records of its occurrence existed until 1986, mainly noting that the adults of this species weigh tens of tonnes, yet only feed upon microscopic plankton, while recent years have brought with them research programmes, tourism, plenty more sightings and a lot more science. Today, many questions still remain. How did such a large animal escape our notice for so long? And how is it that now, with hundreds of papers published, there are still great holes in our knowledge of this species?

Let's start with what we do know. Firstly, there is the prestigious title of the biggest fish in the sea. The largest reported whale shark to date was documented in Taiwanese fishery in 1987 at a giant 20 metres and weighing in at a massive 34 tonnes! With the capacity to reach such a great size, it has been estimated that these animals might live as long as 150 years. Their confusing name often leads many to think of them as whales, not sharks, but the whale part of the name is perhaps more of a nod to its great size, as well as the ecological similarities they share with these mammals, roaming the oceans in search of their planktonic food.

We also know now that these giants are usually found in all tropical and warm temperate seas, usually, with a few exceptions, between the latitudes of 30°N and 30°S. Whale shark sightings have been reported in both oceanic and coastal waters, with much of what we now know and understand about these giant fish being gleaned from seasonal and relatively predictable coastal aggregations of these animals that form at various locations around the world.