Basking sharks have a circum-global distribution in temperate waters normally between 6-16 degrees Celsius (figure1) and are most frequently sighted during the months of April – September in the North Atlantic including Inishowen waters (Matrin & Clark, 2008, CSAS 2008). In the Pacific the basking shark is mainly reported during the winter months, between October – May. Frequent sightings occur on the coast of California especially near the Santa Barbara Channel Islands. There is one published record of a basking shark in Mexican waters and California is usually regarded as the southern end of the shark’s Pacific distribution (Sandoval-Castillo, J. et al, 2005).
Until the late 1960’s they were also commonly sighted and encountered to the North in the Pacific especially in British Columbia. UK based research estimated that they spend up 36% of their time on the surface during this period (Sims et al, 2003). Recent studies have also shown that they do not hibernate during winter months but instead move to deeper waters (up to 1264m below sea level), these waters show similar characteristics to their summer habitat. These stratified feeding waters are associated with continental shelf areas during winter (Gore et al 2008, Sims et al, 2003). They have been recorded to be somewhat habitual in their choice of feeding areas and when returning to coastal waters. Thus supporting theories on how localised population groups are highly susceptible to target fishing (Sims & Reid, 2002). The comparison of public sightings data, dedicated transect survey and satellite tag geolocation results show considerable differences between identified ‘hotspots’ for shark activity and areas of feeding behaviour (Southhall et al, 2005).