Hunting and Feeding: Whale Shark (Rhincodon typus)

The whale shark is the world’s largest fish, growing from 12 – 20m (29 – 66ft.) (Uhlenbroek, 2008). It has an extremely large head, prominent ridges running along its grey or brown body, and artistically patterned with white spots all over (Stevens, 2006). Whale sharks migrate through oceans all around the world to exploit areas of rich feeding (Stevens, 2006). One such destination is Ningaloo Reef situated off the coast of Western Australia, where whale sharks often congregate to feast on the plankton boom resulting from the mass spawning of corals (Uhlenbroek, 2008).

It is thought that whale sharks are able to determine the best feeding areas through olfactory cues (Uhlenbroek, 2008). They feed primarily by cruising slowly through food rich water, passing water through their mouths and out through their gills, effectively trapping food for swallowing, however, whale sharks have also been known to use their mouths as buckets and swim upwards through a dense patch of food (Martin, 2007). The width of a whale sharks mouth when it is opened fully to engulf prey is approximately 1.5m (Uhlenbroek, 2008).

Whale sharks are not the only filter feeding shark; basking sharks and mega-mouth sharks are also highly efficient filter feeders, equipped with large mouths and gill arches (Martin, 2007). In order to catch their prey, whale sharks synchronise gulping in water and opening their gills, they also create suction from which most fish cannot escape, by expanding their buccal cavity or gulping air at the surface (Stevens, 2006). Water that is pumped through the gills, passes through a sieve of bony projections known as gill rakers, and only potential food particular greater than 3mm are trapped (Uhlenbroek, 2008).

References:

Uhlenbroek, C. (2008). Animal Life. Penguin Group, UK.

Martin, R. A. (2007). A review of behavioural ecology of whale sharks (Rhincodon typus). Fisheries Reseach, 84(1), 10-16.

 

Stevens, J. D. (2006). Whale shark (Rhincodon typus) biology and ecology: A review of the primary literature. Fisheries Research, 84(1), 4-9.