15ft sharks are heading for Britain, blame the marine heatwave (2024)

The smalltooth sand tiger shark is an elusive creature, swimming in ocean waters at depths of up to 2,900ft, well away from humans. That is probably no bad thing.

While the species is not aggressive towards humans, preferring to feed on octopus and small fish, bumping into a shark with rows of ragged teeth would be enough to give any swimmer a fright.

But now, for the first time in the scientific record, it has been found in our waters, more than 200 miles north of its normal range. Three of this species of shark have been identified at three different locations around Britain and Ireland this year, according to a group of marine biologists led by the Zoological Society of London (ZSL).

The first sighting, of a 9ft (2.75m) female, was in March at Lepe Beach in Hampshire. The broadcaster Dan Snow, who lives nearby, posted on social media: “So I’m as shark positive as the next woke dude but what in the hell is this fish that just washed up on my local beach where I regularly swim without a care in the world?”

Within weeks, two more sharks from the same species were stranded in quick succession. “We were all a bit shocked by it,” said Dr David Curnick, head of ZSL’s ocean predator lab.

Scientists know very little about this rare deep-water species (Odontaspis ferox), which grows to lengths of 11ft (3.4m) for males and 15ft (4.5m) for females, smaller than great whites, which can grow to 21ft (6.4m).

Dr Nick Payne, an assistant professor at Trinity College Dublin, said these unusual animals are “pretty uncommon, even in the places where they’re the most common”.

Globally, the International Union for Conservation of Nature’s Red List categorises the smalltooth sand tiger shark species as “vulnerable”, with populations in Europe critically endangered. Threats include pollution, coastal development and being unintentionally caught by commercial fisheries.

Strandings can provide important scientific knowledge, which is why ZSL collects specimens for analysis.

The significant discovery in Hampshire would swiftly be followed by another. Around two weeks later, a 14ft (4.3m) mature female was found dead on the rocks at Kilmore Quay, County Wexford, Ireland, in April.

At first, Payne was “pretty sceptical” that it could be another smalltooth sand tiger. But there was no doubt when he saw the distinctive teeth which had one long, pointy central cusp with several tiny cusps of about a millimetre either side. “[The teeth are] long and thin: ragged looking. In fact, one of the common names is the ragged-tooth shark,” he said.

Unlike a great white’s large, sharp, triangular teeth, designed for tearing the flesh off prey such as seals, scientists associate these teeth with a diet of smaller fish, octopus and crustaceans.

In May, a third smalltooth sand tiger shark — a 10ft (2.9m) male — was found floating on the water’s surface by a fisherman in Lyme Bay, Dorset.

These three sightings are believed to be the species’ most northerly occurrences, superseding an unconfirmed report in Normandy in 2012. While their exact range is unknown, these sharks usually live in temperate and tropical waters around remote islands and continental shelves where they can access deep waters.

They have been observed in locations including Tanzania’s Pemba Island, New Zealand’s Kermadec and White islands and Colombia’s Malpelo Island but, until now, were believed not to travel further north than the Bay of Biscay.

What could have caused these sharks to expand their range hundreds of miles north? “We think it’s indicative of climate change,” said Curnick.

Large-bodied sharks tend to move in a seasonal pattern, often driven by environmental conditions, such as water temperature. The researchers, whose findings are published in the Journal of Fish Biology, said the summers of 2021 and 2022 saw seabed temperatures in the British Isles reach an average 12.5C, more than 1C higher than a decade previously. This year, a marine heatwave has also caused North Sea water temperatures to rise far above normal, which experts believe has disrupted underwater ecosystems.

The researchers said these “unseasonably warm” conditions may have driven the sharks to travel outside their usual range. “What it doesn’t resolve is why they all suddenly died,” said Curnick. Starvation didn’t seem likely, he said, as the bodies all seemed “in reasonable condition” and without noticeable bodily wastage. The male shark showed evidence of tangling with fishing gear but there was no strong evidence the deaths were caused by commercial fishing.

Finding three individuals of such a rare species within a short space of time was surprising. But it may not be a one-off. With many species changing their migration pattern in response to warming temperatures — July was the planet’s hottest month on record — smalltooth sand tiger sharks might continue to visit UK and Irish waters.

“With the pace at which temperature is changing out there at the moment, it would be more surprising if we don’t see events like this happening more and more,” said Payne.

And it may not just be this species moving into our seas.

British waters are already home to basking sharks — the world’s second-largest shark — as well as blue sharks and shortfin mako sharks, which visit our shores during the warmer months of the year as part of their seasonal migration. There has been speculation that a warmer Britain might also create the right conditions for great white sharks. There are already plenty of seals in our waters, which are among their preferred prey. But the Shark Trust has repeatedly dismissed these claims. “As exciting as that would be, it’s very unlikely,” it said. “There have been no confirmed sightings or strong evidence to suggest they’re here.”

But if smalltooth sand tiger sharks might keep appearing in our waters, should people be concerned?

Put simply, no. Although these large sharks look intimidating, “they’re completely harmless and benign to humans”, said Curnick. There are no recorded instances of smalltooth sand tiger sharks biting humans.

Payne agreed. “I would fall off my chair if I ever heard a report of an unprovoked attack by this kind of animal,” he said. “I certainly won’t be swimming around the south coast of Ireland looking over my shoulder.”

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