Basking Shark Diet

Zooplankton © Uwe Kils.Basking Sharks are one of only three filter-feeding sharks – the others being the Whale Shark (Rhincodon typus) and the Megamouth Shark (Megachasma pelagios). The Basking Shark may be unique, however, in that it is the only one that feeds entirely passively by swimming through water with its mouth open rather than actively sucking in water for filtering.

Prey items consist primarily of zooplankton – including small copepods (typically Calanus helgolandicus), barnacles, decapod larvae, fish eggs and a deep-water oceanic shrimp (Sergestes similis). Movements of Basking Sharks are driven by zooplankton growth, with studies combining satellite tracking of sharks and remote sensing (satellite photography) of plankton blooms demonstrating that Basking Sharks are able to locate plankton ‘hot spots’ over ranges of some 500km. The big question is: can Basking Sharks detect plankton blooms over great distances or have they learned to feed in particular areas at certain times?

Basking Sharks are often observed swimming, mouth agape with their gills distended; only closing their mouth occasionally to swallow the prey items trapped by their gillrakers (long comb-like structures on the gills that filter zooplankton from the water). The gillrakers are assisted in their capture of plankton by mucus secreted in the pharynx and can strain up to 2000 tonnes of water per hour resulting in Basking Sharks having, on average, around half a tonne of food material present in their stomach.

The common name of the Basking Shark comes from the fact that whilst feeding it appears to be basking at the surface, its first dorsal fin fully exposed and it’s back partly exposed.