Image of basking shark courtesy of Scottish Natural Heritage
Seas between the islands of Skye and Mull on Scotland’s west coast are highly important for basking sharks, according to a report published earlier this month by Scottish Natural Heritage (SNH).
Each year large numbers of basking sharks are seen in an area off the Sea of the Hebrides which is currently being assessed as part of the Scottish Marine Protected Areas Project.
The report sets out findings from the first two years of a project which aims to reveal some of the mysteries surrounding the world’s second largest fish. The project is a joint venture between SNH and the University of Exeter (UoE), and is the first known to use satellite tagging technology to track the near real-time movements of basking sharks.
Twenty sharks were tagged in summer 2012 and a further 31 were tagged a year later. In both years the tagged sharks spent most of July, August and September in waters around the islands of Coll and Tiree and the Hyskeir lighthouse. In these months more than 80% of the satellite transmissions received from tagged sharks came from within the Sea of the Hebrides. This is seen as further evidence that the area is a special place for these sharks.
Scientists at SNH and UoE believe the sharks return each year to feed in the area’s plankton-rich seas but the sharks’ behaviour suggests they might come for other reasons too.
Dr Suzanne Henderson from SNH, who is managing the project said: “As well as cruising around and feeding at the surface they can be seen showing courtship-like behaviours, such as jumping clear of the water, known as breaching and swimming around nose-to-tail. These social behaviours suggest that the sharks return to the area not just to feed on the plankton bloom but for other reasons too, perhaps even to find a mate.”
Information received from the tags also shows that the sharks spend these summer months at different depths, moving up and down in the water on a daily basis. A large proportion of their time is spent in shallow water less than five metres deep, but they also spend time in deeper water down to 250 metres. There doesn’t seem to be a single pattern to this daily vertical migration, and it appears that the sharks adapt their behaviour to local conditions.
Information from the tags is fed to a website where people can follow the sharks’ movements. After a few months the tags tend to fall off but some of the tags attached in 2013 are still on the sharks.
Some of the tags contain additional information which is not transmitted, so it’s important that these are retrieved. Anyone who finds a tag around the UK’s shores should get in touch. There is a reward available for each tag returned.
The tags are silver grey, torpedo shaped and 15 to 18 cm in length with a small antenna. If found please pick up and contact the SNH office in Oban on 0300 244 9360, or email.
For more information on the project and to follow the movements of the tagged basking sharks online, go to the website