Swimming Speed & Style

Basking Sharks ordinarily cruise at around 2.5 to 4 mph however they are sometimes seen leaping completely out of the water and must be capable of reaching much faster speeds to be able to do so. The reason for Basking Sharks breaching like this is unclear although a commonly cited theory is that this is done to dislodge parasites, lampreys or remoras. However it is more likely that breaching is linked to courtship or mating behaviour either as a method for demonstrating fitness or receptiveness to mating.

 

 

 Feeding

 

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, as 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 of 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 and satellite tracking of sharks when related to remote sensing of plankton has demonstrated that Basking Sharks are able to locate plankton ‘hot spots’ over ranges of about 500 km (Sims et al. 2003). The big question is, can the sharks perceive plankton blooms over great distances or have they learned to feed in particular areas?

 

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 comblike 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.