A great white shark called Lydia has become the first of its species to be observed crossing from one side of the Atlantic into the other.

The satellite-tagged fish crossed the mid-Atlantic ridge, which marks a rough boundary line between east and west.

She has now turned towards the UK, but it’s unclear where she’ll go next.

But the expedition leader for the project tracking Lydia said he thought she was pregnant and headed for birthing grounds in the Mediterranean.

Chris Fischer, who is also founding chairman of the Ocearch shark tagging venture, said that if Lydia continued on to Europe or Africa, she would likely become “more coastal”.

“I certainly think that it’s possible for Lydia to make it to the UK,” he said, but added that he couldn’t know if that was where she was headed.

“There have been sightings in the past [in the UK], but I think these were anecdotal versus a documented presence. So hopefully we’ll be able to help with that.”

It’s often been argued that the waters of these isles are too cold for the sharks, but the Ocearch founder cast doubt on this.

“One thing we have learnt just in the last year with sharks in the Atlantic is what we used to think was too cold simply is not,” he said.

“Lydia has come over from Nova Scotia in Newfoundland [Canada]. These sharks have the capacity to deal with very cold water temperatures for long periods of time.”

But, he said: “If I had to guess, I would guess that Lydia is pregnant, and that she has been out in the open ocean gestating her babies and that this spring she will lead us to where those baby white sharks are born – the nursery,” he said.

Mr Fischer, who has led numerous ocean expeditions, added: “If you forced me to guess where that was, I’d say it was over in the Mediterranean, near Turkey… but that’s longball I’m playing. She could turn around right now head back to Florida.”

He said that small white sharks had been observed in the Aegean Sea before, but he said scientists working on the team did not share his view. This was because preliminary analysis of blood samples from Lydia suggested she was not pregnant at the time of her tagging.

But Mr Fischer defended his theory, saying there were still uncertainties over the way that white sharks became pregnant, adding: “The sperm from the male comes in a packet with a shell on it. They can carry it around for a while until a special organ inside them breaks down the shell and they get pregnant,” he explained.

“We know it’s 18 months from when we discover the breeding aggregation to when they lead us to the nursery… what we don’t know is how long do they carry that sperm packet and how long is it until their body breaks down the shell.”

Lydia is now roughly 1,600km (1,000 miles) from the western coasts of Ireland and Britain, and nearly 4,800km (3,000 miles) from Jacksonville, Florida where the tracking device was attached to her in March 2013.

In total, the young female shark has travelled more than 30,500km (19,000 miles) since last year.

The Ocearch project was initiated to gather data on the movements, biology and health of sharks for conservation purposes as well as for public safety and education.

The scientists have been using a custom-built 34,000kg (75,000lb) capacity hydraulic platform, operated from their research vessel the M/V Ocearch, to safely lift mature sharks so that researchers can tag and study them.

Lydia was on the platform for 15 minutes, during which researchers extracted blood for analysis and performed an ultrasound examination, in addition to attaching the tag.

Mr Fischer described Lydia as “super-healthy” at the time of her tagging. “I would say she’s just been sexually mature for a short period of time, which would put her in her 20s,” he said.

“She looked like she had a bright future ahead of her – never would have dreamed she would lead us over to your neighbourhood.

“It just shows that if we’re going to look after some of these magnificent apex predators – the lions of the oceans – we’re all going to have to work together. No one country can do it.”

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Source: www.bbc.co.uk/news