Octopus scientists seek fishing community stories

Dr Simon Thomas is trying to understand why octopus numbers have exploded for the second time in four years

Scientists studying an explosion in octopus numbers in waters off the Channel Islands and south-west England want members of the fishing community to share their experiences to help them understand why it is happening.

Dr Simon Thomas, from the University of Plymouth, said this year's increase - known as a bloom - was unusual as it was the second in four years, whereas normally they happened every 50 to 70 years.

He now wants "first-hand" accounts from people in the fishing industry, especially those catching crabs and lobsters.

Dr Thomas said: "I work on the theory that if you spend every day out there doing your living, you probably know a lot more about your area than I do."

Common octopus (Octopus vulgaris) numbers have risen sharply since early this year.

Now Dr Thomas's team has started working with the Marine Biological Association and Plymouth Marine Laboratory to understand why.

He said this year's bloom started off the French coast, before moving to the Channel Islands and then to the south coast of England.

Dr Thomas said environmental factors like medium-term water temperature trends were "probably" partly to blame, but "we don't know a lot of the reasons why this happened".

The explosion in octopus numbers has made catching lobsters and crabs harder

Crab and fishing catches had "completely collapsed" where octopuses were present, he said.

"Some of these pots will have 10 or 12 octopus in them - and why they're doing that we're not entirely sure."

He explained the behaviour was unusual as they were "normally a solitary species".

He said: "To give you a bit of context, octopus are sort of the ultimate exponents of 'live fast, die young'.

"So, they rapidly grow, they only live a couple of years and they produce a lot of offspring, [which end up] in the plankton."

Dr Thomas said fishers were "absolutely vital" to understand why the bloom was happening, and he hoped the information could help them adapt if it became a more regular trend.

Some fishers were already adapting by catching octopuses, such as "one of the largest ever catches" which landed in Newlyn, Cornwall, recently.

However, he said small-scale fishers could struggle to sell catches.

"It's decimating some fishermen's livelihoods, which is never a good thing."

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