Scientists dismiss likelihood of species arriving in Britain but bluefin tuna are on the rise
— Britain’s westerly waters are experiencing a bumper season for sightings of bluefin tuna, while visitors to Cornwall have been thrilled by the unusual sighting of a blue shark swimming in St Ives harbour.
But anyone hoping for sightings of great white sharks in British waters are likely to be disappointed, despite a spate of scare stories that began after a researcher at the University of Southampton predicted that 10 shark species new to the UK could reach British waters by 2050. Dr Ken Collins made the prediction as part of a report to promote a TV channel’s shark series.
Earlier this year, scientists published evidence that tiger sharks off the coast of eastern Australia were most abundant in sea temperatures of 22°C (72°F), with less activity at higher and lower temperatures. Collins looked at other recent studies to compile a list of 10 possible new arrivals, including the great hammerhead, blacktip and bigeye thresher – but not the great white.
According to Richard Peirce, a shark campaigner and author, rising sea temperatures around the UK will not increase the likelihood of great whites arriving. “Most experts agree that the real conundrum with great white sharks is not whether they are likely to start rocking up but why they are not here,” he said. “Our conditions in Britain are already perfect and warming waters are not going to help them.”
Peirce has investigated nearly 100 claimed sightings of great whites in British waters and found fewer than 10 of them to be credible. Marine biologists say there is no scientific evidence of great whites arriving – and no risk of shark attacks.
Last year saw what some say is the first British shark attack on a surfer when a man was left with a bloodied thumb after encountering a 3ft-long smooth hound shark.
This month, footage of a blue shark swimming in St Ives harbour excited locals in Cornwall and experts, who say this pelagic – deep water – species is more commonly found 10 miles offshore.
“Occasionally you’ll see a blue shark at the surface but they are certainly never patrolling the beaches looking for a tourist to eat,” said Hannah Jones of Marine Discovery, who runs wildlife watching trips from Penzance. “All this talk of sharks along the coast – the only sharks you’re likely to see are basking sharks.”
Though 2018 has been a poor year for sightings of basking sharks in Cornish waters, according to Jones, over the past three years her boat has encountered many more common dolphins as well as bluefin tuna.
“Bluefins were always here. Then they got hammered for fishing before EU controls have really helped bluefin stocks recover,” said Jones. “People think that tuna are little and come in tins. A bluefin can be bigger than a dolphin. If they are feeding en masse, charging through bait fish, they break the surface and you get this writhing mass of fish. It’s utterly spectacular, like nothing you’ve seen – a tsunami of tuna charging towards you.”
She added: “In the 1970s and 80s it was all Jaws fever. Most people are more sensible, and now if they see a shark it’s a massive privilege rather than anything scary. There have always been sharks here and in years gone by there would have been many more.
“We may perhaps start getting more southerly species, such as some species of hammerhead perhaps, but given that Cornwall is such a crossroads in terms of water temperature and salinity, many things would be possible. It doesn’t mean it’s likely.”
According to Dr Phil Doherty, a researcher at the University of Exeter who is investigating what influences the movement and migration of sharks, rising sea temperatures will not automatically lead to new species arriving because it is not yet known what tolerance different shark species have for different water temperatures, or how prey species may be affected by warmer waters.
He said: “Some studies are showing plankton blooms starting to shift polewards in reaction to temperature changes. We might see other species moving in response to prey movements but it’s not something we can say for certain.”
Doherty also warned that Atlantic fishing – unregulated in the high seas – continued to be a check on shark species reaching British waters. “We still have very high levels of fishing, particularly for sharks in the Atlantic, and we have very little regulation of the catching of sharks,” he said. There are no limits for the number of blue shark and shortfin makos that can be caught by fishing vessels. “The by-catch level is huge for some of these sharks,” said Doherty.
Shark populations have fallen by up to 90% globally with 70 species classified as vulnerable – including the great white shark – or critically endangered.
Peirce said he supported the logic of Collins’ predictions, and new shark species could be a small positive to climate change. “Here are some wonderful new marine species that are going to be inhabiting our waters. It should not be a cause for fear and quaking but a cause for celebration.”
by Patrick Barkham | The Guardian