An area off the west coast of Scotland has been shown to be important to the second largest fish on the planet, which can be literally as big as a bus.

A pioneering three-year project to learn some of the secrets of Scotland’s basking sharks by using satellite tag technology, has established they spend most of their summer in the Sea of the Hebrides.

They return to the same area the following year, according to the final project report published by Scottish Natural Heritage (SNH).

Measuring up to 40ft, the basking shark is the second only to the giant whale shark in size.

Between 2012 and 2014, some 61 basking sharks were tagged in the ground-breaking project, a partnership between SNH and the University of Exeter (UoE).

Tags were attached to the sharks near the islands of Hyskier, Coll and Tiree, where each summer large numbers can be seen feeding near the surface. The tagged sharks were particularly drawn to the waters around these islands.

Scientists at SNH and UoE believe the sharks return each year to feed in the area’s plankton-rich seas. The sharks’ behaviour suggests the waters could also be important to the sharks for other reasons and that they could benefit from a proposed Marine Protected Area (MPA) off the west coast.

Suzanne Henderson from SNH, who is managing the project said:

“It’s been really exciting to learn that the same individual basking sharks return in consecutive years to use Scottish waters. It’s something we thought happened - but we now have the first proof that this occurs. It really does emphasise that the Sea of the Hebrides is highly important for this migrating species.”

She said protecting highly mobile species, such as basking shark and whales, was difficult due to the large areas they covered. So identifying and managing areas where the animals gather to feed, or for important life-cycle events, such as courtship, could play an important role in their conservation.

As part of the Scottish MPA Programme, SNH has recommended that an area of the Sea of the Hebrides from Skye to Mull be designated an MPA to protect the basking sharks, and also minke whales. Scottish Ministers are currently considering the proposal.

Ms Henderson said:

“As well as cruising around and feeding at the surface the sharks 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.”

She said from autumn onwards the tagged sharks dispersed widely, leaving the shallow coastal waters for deep sea. Some were seen to head south as far as the Iberian Peninsula and North Africa, some headed west of Ireland and others remained relatively close to Scotland throughout the winter.

Cabinet Secretary for Rural Affairs, Food and the Environment, Richard Lochhead said the basking shark, was an iconic species for marine conservation. "The results of this valuable work will help us along the path of getting the Marine Protected Area network right by ensuring the ecological processes and places basking shark depend upon are afforded the protection they need to endure.”