Octopus boom off UK coast down to 'perfect storm'

Octopuses, sharks and tuna that are booming in the sea around the UK could be part of a fundamental shift in the marine environment, a leading scientist has told Sky News.

Dr Simon Thomas, from the Marine Biological Association in Plymouth, said a perfect storm of factors, including climate change and overfishing, is leading to a rapid change in the species being found around the coast. "Since 2016, you've seen a lot of our traditional fish, like cod, ling and pollock decreasing in numbers and pushing northwards," he said.

"Then we've seen other fish, especially things like bluefin tuna and blue sharks, being found in huge numbers in the water here. "It's almost like you've seen a complete shift in the regime of the ocean." 'I've never seen anything like it' Fishermen on the south coast of Devon and Cornwall are currently catching huge numbers of a large octopus species that is normally rare in the UK.

"I've never seen anything like it in my lifetime," said Dr Thomas. "I've spent 40 years at sea and probably seen three or four of the big octopus over the years.

Now they are seen regularly and (crab fishermen) are reporting their pots have been decimated." The octopuses are raiding crab and lobster pots for an easy meal. But there are so many of them, and they are so hungry, that fishermen say they are eating not only the bait and crustaceans, but also, at times, each other.

Sam Jago, skipper of the Bosloe, returned to Plymouth after a day's fishing with 11 crates of octopuses - a 400kg bonanza that could fetch almost £3,000 at market rates. But he had just over one tub of crabs and lobsters - when normally he'd have more than a dozen.

"They crack the shell and suck everything out of it," he said. "It's a quick buck at the moment, but who knows how long it's going to last for.

"They will stay here until they've eaten everything. "But if the octopus go, the crab isn't going to just appear out of thin air.

"We won't have a great deal to catch." Read more from Sky News:Trooping the Colour - see best picsIs Ibiza at breaking point?Why is Ballymena the site of riots? The Marine Biological Association is studying factors that could underpin the surge in octopus numbers. The sea around the UK is around 2C warmer than normal.

But in the southwest of England the temperature is 3C or even 4C above average for the time of year. Dr Thomas said warmer waters increase survival of young octopus fry over winter, and a change to ocean currents could bring them more food.

'The ocean is changing' Overfishing of species that would normally eat young octopuses may also mean more are surviving to adulthood. "There is no doubt that the ocean is changing," he said.

"Fishermen are like the canaries in the coal mine, the first to see things changing out at sea." Scientists say protecting key parts of the ocean as marine nature reserves would serve as a buffer against pressures from human activity elsewhere. So far, 50 nations plus the EU have ratified the United Nations High Seas Treaty that commits countries to protect 30% of the ocean by 2030.

Another nine need to ratify it for it to become operational. The UK government has said it will ratify the treaty by the end of the year..