Are bright blue lobsters as rare as once thought?

Blue lobsters have a genetic mutation which produces the vivid colour

Bright blue lobsters have long been considered one of nature's wonders, widely touted as a one-in-two-million find. But scientists and hatchery experts are now questioning whether these beautiful electric blue crustaceans are truly as rare as once was believed.

Why do lobsters turn blue?

The colour of a lobster's shell is the result of a complex interplay between two compounds, according to Prof Jamie Stevens of the University of Exeter.

They are:

• Astaxanthin, a red pigment that lobsters absorb from their diet

• Crustacyanin, a protein that binds with astaxanthin to produce a blue hue

In most lobsters, this combination results in a dark, muddy blue-green shell that helps them blend into the seabed.

A blue lobster on the left compared with its more common relative on the right

When the balance shifts, either due to genetics or environmental factors, the colour can become dramatically more vibrant.

"When we talk about blue lobsters, we're often seeing extra blue lobsters," Prof Stevens said.

"These are lobsters with a genetic mutation that causes an overproduction of crustacyanin, giving them a vivid, electric blue appearance."

What role does environment play?

Chris Weston, senior hatchery technician at the National Lobster Hatchery in Padstow, Cornwall, has observed colour changes in lobsters raised in captivity.

"We've had several lobsters hatch here and grow up with that electric blue look," he said.

"Interestingly, when we deploy them into containers in the sea, they often shift to a darker, more natural blue. But when they return to the hatchery, they become lighter again."

Mr Weston believes this may be due to environmental factors such as light exposure, as hatcheries may be brighter than the seabed, influencing pigmentation.

Light exposure at hatcheries may affect pigmentation, says Chris Weston at the National Lobster Hatchery

He said it could also be down to dietary variation, as lobsters in captivity may have less access to astaxanthin-rich food, allowing the blue crustacyanin to dominate.

Similar environmental changes could be happening in the wild, potentially contributing to the rise in sightings of blue lobsters, he added.

Are blue lobsters still rare?

Prof Stevens said reports of blue lobsters were increasing.

"There's been an uptick in sightings," he said.

"We haven't seen a huge rise in our own samples, but fishermen are reporting more of them."

One possible explanation is the mutation is being passed on more successfully.

"If these lobsters are surviving and reproducing, they're passing on that trait," he said.

Ben Marshall, head of production at the hatchery, said: "It seems they may not be as rare as we thought.

"It was thought that the blue lobsters are as rare as one in two million, but with the average catch in Cornwall of roughly half a million individual lobsters landed each year, we should only see one blue lobster every two years."

Experts are urging more research into blue lobsters

Historically, brightly coloured lobsters were thought to be more vulnerable to predators, especially when young or moulting. Their vivid shells made them easy targets.

Prof Stevens said: "If they're increasing, something in their environment may have changed, perhaps fewer predators, or better camouflage in new habitats."

He added he did not believe there was a link to climate change.

"The crustacyanin, the blue colour, is under the control of two genes and we don't see any relationship with those genes and anything that might constitute a trend towards changes in climate," he said.

What is next for research?

Prof Stevens and Mr Weston agree more research is needed on whether numbers are rising.

Genetic studies, environmental monitoring, and collaboration with fishermen could help scientists understand whether blue lobsters are truly becoming more common, and why.

Beshlie Pool of the South Devon and Channel Shellfishermen, said it would be "really useful to have a recording scheme", the last known catch of a blue lobster in the south Devon water was 12 months ago.