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Tagged basking shark from Irish waters spotted in Scottish seas for mating

By Mike Merritt

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Basking sharks feed off plankton and many are seen off the west coast of Scotland each year. Picture: Simon Burt/westcountryphotographers.com/Adobe Stock
Basking sharks feed off plankton and many are seen off the west coast of Scotland each year. Picture: Simon Burt/westcountryphotographers.com/Adobe Stock

It is a long way to go to find love. A basking shark tagged off County Clare in Ireland has been re-sighted months later off the west coast of Scotland looking for a mate.

The shark was tagged on April 25 with a numbered, red-coloured tag off Kilkee and was re-sighted nearly 600km (373 miles) further north on August 19 in the Sea of the Hebrides.

This re-sighting record, 116 days after the tag was deployed, confirms the connectivity between Irish and Scottish waters – which is believed to be a breeding hotspot for the sharks.

Dr Simon Berrow of the Irish Basking Shark Group, which tagged the shark off west Clare, said: “We have long been aware that sharks in Irish waters are moving north through the early summer along the west coast and into Scottish waters, but this is the longest duration between re-sightings of our simple shark tags, which is fantastic and encouraging.”

The tagged shark was observed by snorkelling with Basking Shark Scotland.

Founder Shane Wasik said: “This is the third Irish tag we have recorded in recent years and it gives us a great sense of purpose to contribute to this Irish conservation-led research project. The passengers were very excited to discover the tag and were so pleased to hear about the match from IBSG group. We welcome future scientific collaboration to assist in the understanding of this species and work towards protection over their entire Atlantic migration.”

Dr Emmett Johnston, who works closely with Dr Berrow on the long-running Irish shark tagging project, said: “Basking sharks first appear in inshore Irish waters in the early spring between April and May, but generally appear later off the west coast of Scotland. This is thought to be linked to the later zooplankton bloom further north off of Scotland – these plankton are the sharks’ main prey.

"This research is important to demonstrate that these sharks cross international boundaries and any management needs to consider their whole range. Basking sharks are protected under a suite of legislation in the UK including Scotland and Northern Ireland."

The Sea of the Hebrides is also proposed as a Marine Protected Area for basking sharks by the Scottish Government.

Britain's biggest fish come to Scotland mainly to find a mate, recent research revealed.

Basking sharks are usually spotted sunning their giant fins at the surface, but it seems they prefer to spend most their time near the seabed, says the scientific study.

And it adds weight to the theory that the sharks come to Scotland not to feed but to breed.

The first study to successfully track a basking shark using a robot camera has shed new light on the behaviour of what is also the world’s second largest fish.

An autonomous ‘SharkCam’ underwater vehicle (AUV) was deployed in the UK for the first time last summer to observe and gather footage of the behaviour of basking sharks in the Inner Hebrides.

Little is known about the underwater behaviour of the globally-endangered species, despite basking sharks being prevalent in the waters off the west coast of Scotland.

The SharkCam followed three basking sharks below the surface of the water, collecting video of their behaviour from a distance as they swam off the coast of Coll and Tiree.

The international team of researchers recently published their findings in the journal Animal Biotelemetry.

Detailed examination of the footage revealed the sharks spending an unexpected amount of time swimming near the seabed – a behaviour which has not often been reported for the species.

Notably the sharks were not seen to be feeding.

Dr Suzanne Henderson, NatureScot marine ecosystems manager, said: “While we weren’t lucky enough to capture courtship or mating behaviour on camera this time, this innovative study has shed more light on the lives of these spectacular giant fish.

“The fact that the sharks spent much more time swimming just above the seabed than we previously thought, and with their mouths closed, is really interesting, particularly as the species is often seen as a pelagic or near-surface filter feeding shark. It suggests we may have to rethink not only how many basking sharks are in Scottish waters, but why they are here, as it’s likely not only the plankton they come for.

“The insights the technology has provided about the habitats the sharks use are also invaluable, and will help inform how we protect and conserve the species in future.”

The area is one of only a few world-wide where large numbers of basking sharks are found feeding in the surface waters each year.

Scientists from NatureScot – formerly Scottish Natural Heritage – and the University of Exeter have previously attached satellite tracking tags to dozens of basking sharks in the Inner Hebrides, as part of a £147,000 project.

The tagging project, which began in 2012, was set up to find out more about the life cycle of the large numbers of sharks that gather around the islands of Coll, Tiree and Canna every summer – an area considered a 'hot spot' for loved-up basking sharks seeking a mate.

One was tracked from Scotland to the Canaries.

Basking sharks can grow up to 36 feet in length – the length of a double decker bus – and seven tonnes in weight but they feed entirely on plankton, tiny animals that drift through the water. The plankton pass through their enormous gaping mouth and are filtered out by their comb-like gills.

They are long lived, with some surviving as long as 50 years. Because they are slow moving, slow to mature and long lived, they are very vulnerable to human disturbance and impacts.

Basking sharks were once hunted by Ring of Bright Water writer Gavin Maxwell around Skye for their oil and meat.

Maxwell set-up a basking shark fishery off the west coast and wrote his first book, Harpoon at a Venture, about how he disastrously hunted the great fish.

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