Local Basking Shark Discoveries

Local discoveries through the work of the former Manx Basking Shark Watch

A brief history of Manx basking shark sightings

It is well known among the Manx community that the Isle of Man was a former hot spot for basking sharks. Tales from older fishermen tell of there being so many basking sharks on our west coast that you could “almost step across them to get back to shore”. These stories date back to the 1960’s when the Manx herring fishery was strong, and basking sharks continued in good numbers into the 1990’s and 2000’s. It was during this time that Ken Watterson set up the original Manx Basking Shark Society.

In 2004 Manx Basking Shark Watch was set up by Jackie and Graham Hall. This was the first public sightings report scheme for basking sharks in Manx waters with the aim of estimating relative abundance and distribution around our island. Within the first few years of study, the following patterns begun to emerge:

Basking shark hotspots on South and Southwest coast of the Isle of Man
Most sightings mid-May to mid August
Basking shark schools coming through Manx waters in waves
Putative courtship behaviour
Shark sizes from 1.5m to 8.0m (newborn-mature)

Tagging programme

Manx Basking Shark Watch’s tagging scheme ran from 2012-2017 with the aim of finding out where our sharks migrated to and whether there was any residency to the Isle of Man.

Tagging results showed a highly varied distribution, with some sharks heading to Irish and Scottish waters, and others as far as Norway, Morrocco, Portugal and North Africa. One shark made the return journey across the North Atlantic to Newfoundland, twice.

Tagging stopped in 2017 due to the decrease in shark numbers. In 2022, three remaining SPOT tags were given to researchers in Ireland and deployed off Achill on the west coast.

DNA and shark passports

Between 2009 and 2017 DNA sampling was carried out with slime samples collected for genetic testing. The creation of ‘basking shark passports’ began. The following data was collected on mature sharks under a strict licence from the Department Of Environment, Food and Agriculture.

Take ID photo taken of dorsal fin
Find the sharks gender using underwater camera
Estimate the shark’s length
Obtain DNA sample
Satellite tag the shark

Basking shark decline

Since 2010, basking shark numbers have decreased dramatically in Manx waters. We went from around 500 sighting reports per season in 2010, to 8 in 2021, 68 in 2022 and 17 in 2023

We have to remember that with all aspects of nature, there are natural variations- fluctuations and cycles, changes in plankton distribution and tidal currents.

Whilst fewer basking sharks visit Manx waters, they are still present in other areas of the British Isles. In recent years the west coast of Ireland has seen what is thought to have been huge courtship gatherings.

For more information on basking sharks in different regions see our links page.

Timeline of MBSW & MWDW

Report a Sighting

Have you seen a basking shark in Manx waters? Report your sighting to us.