It was previously thought that Basking Sharks hibernated during the winter due to a number of circumstantial pieces of evidence mainly their disappearance during the winter months and that the liver weights of fishery caught Basking Sharks was much less in the spring than in the autumn indicating a cessation of feeding. This was supported by reports that the sharks shed their gillrakers over the winter and so were presumably incapable of feeding.

 

 Tall Tails - Read about some of the myths associated with Basking Sharks

 

 

Recent studies (Sims et al. 2003, Francis & Duffy 2002) have disproved the theory that Basking Sharks hibernate and have proven that the sharks are very active throughout the year. It was determined that, in the winter months, rather than spending time near the surface Basking Sharks spend more time in deeper water at depths of up to 900 m feeding on deep water plankton communities. Using satellite tags Sims et al. also discovered that Basking Sharks still move thousands of kilometres during the winter months actively tracking plankton blooms in order to feed.

 

Furthermore, it was determined that Basking Sharks do shed their gillrakers but not all in one go. Rather than losing their gillrakers all in one moult, over the winter months shedding and re-growing new gillrakers is an ongoing process.
 
More recently satellite tagging studies undertaken on either side of the Atlantic have demonstrated some unique behaviour never before seen in Basking Sharks.
 
Gore et al (2008) tagged a shark off the Isle of Man which promptly headed straight for Newfoundland demonstrating the first trans-atlantic migration recorded by a Basking Shark whilst also reaching never before observed depths of over 1200 metres.
 
Skomal et al (2009) tagged some Basking Sharks off New England which headed South, crossing the equator and into waters of the Southern Hemisphere where they spent time at depths of between 800-1000m.
 
These two important pieces of work have demonstrated that neither the equator or the Atlantic Ocean represent barriers to the movement of Basking Sharks and pose important questions regarding the population size and genetic mixing of Basking Sharks in the Atlantic and further afield. These novel studies also highlight the need for global, rather than solely regional, protection for these sharks.

 

 

Basking Sharks are apparently quite social animals and are seen singly, in groups or in schools of hundreds of individuals feeding in areas of high plankton concentration.

 

Fisheries captures of Basking Sharks off the British Isles during the summer revealed that the individuals there were predominantly adult females, outnumbering the males by as much as 40:1, however the few individuals that were caught during the winter were mostly males. Throughout the geographical and vertical migrations that these animals make there are many reports of groups of same size and sex individuals which suggests a strong sexual and population segregation within the species.