Feature: Don't throw a wobbly if you spot some jellyfish

With their long tentacles and indiscriminate stinging, jellyfish are rightly feared by beach-goers. Now Scotland's coastlines are braced for waves of invading jellyfish over the summer, as rising sea temperatures provide ideal conditions for the creatures.

According to experts, numbers of lion's mane, moon and other species of jellyfish could hit record levels in British waters this year.

Last month, around 500 moon jellyfish were washed up on Portobello beach, with similarly large numbers reported at East Beach in North Berwick.

The Marine Conservation Society (MCS) confirmed that as seas warm up, even more jellyfish are expected to bloom over the summer.

MCS biodiversity programme manager Peter Richardson says: "There is strong evidence to suggest that jellyfish numbers are increasing in the Irish Sea and North Sea, so we will probably see more jellyfish in and around the coastal waters of Edinburgh. It wouldn't be a big surprise."

The increase has been linked to factors such as pollution, over-fishing and climate change. But is the spike in jellyfish entirely a bad thing?

"If we start harvesting jellyfish ourselves, then maybe we can benefit in that way," says Dr Richardson. "But that's not necessarily a good thing because then we are fishing down the food chain, and if our fishermen started depending on jellyfish because there were no fish, we really have hit rock bottom."

At the start of the year, UN scientists reported that a rise in carbon dioxide output was making the world's seas more acidic and warned that a side-effect could be a huge rise in jellyfish numbers because they are among the few ocean creatures unaffected by a change in acidity.

Although research into jellyfish is relatively new, Dr Richardson believes the increase should be taken as a warning to start treating our seas better.

He says: "We should consider jellyfish populations as important indicators of the state of our seas. We need to manage our fishing in a sustainable way; to ensure that our seas are sustainable.

"At the moment, jellyfish are doing good but other species are in decline.

"There are places where, on a seasonal basis, fishermen can't fish anymore because their nets get caught in jellyfish. I'm sure there are fishermen in the Lothians with the same problem."

It's not just fishing that jellyfish can affect. Last month, both reactors at the Torness nuclear power station were shut down after huge numbers of jellyfish were found obstructing cooling water filters.

Dr Richardson warned that a similar situation could occur at other nuclear power stations.

"It's happened once and if these jellyfish are occurring in big enough numbers, it can happen again," he says.

However, local beach-goers are being urged not to panic as not one of the jellyfish normally found in UK waters is lethal.

"You can see the moon jellyfish in huge numbers along the coast of Fife and East Lothian," says Dr Richardson. "Most of the reports we get are from people who spot them on the beaches.

"Moon jellyfish are harmless so there's no need for people to not visit the beach.

"There are also strandings of the blue jellyfish. The blue jellyfish and the moon jellyfish are not particularly strong swimmers, and are very much dependent on tides and currents.

"There are thousands of blue jellyfish washing up on some beaches in Fife."

The MCS is urging coastline visitors to take part in its national jellyfish survey by reporting their findings to help understand more about where and when jellyfish occur around the UK.

However, beach lovers are being warned to "look but not touch".

BLUE

Up to 30cm. Similar shape to lion's mane variety but smaller with a blue bell, through which radial lines can be seen. Mild sting.

Sting rating 1/3

LION'S MANE

From 50cm to 2m in diameter. Large, reddish brown umbrella-shaped bell with a mass of long, thin hair-like tentacles. Moderate sting.

Sting rating 2/3

MAUVE STINGER

Up to 10cm. Has a deep bell, pink or mauve warts, 16 marginal lobes and eight marginal, hair-like tentacles. Moderate sting.

Sting rating 2/3

MOON

Up to 40cm in diameter. Transparent, umbrella-shaped bell, edged with short hair-like tentacles. Recognised by the pale purple rings in the bell.

Sting rating none

BY-THE-WIND-SAILOR

Not a jellyfish, but a floating, solitary hydranth. Up to 10cm long and blue-purple in colour. A mass of small tentacles surrounds the mouth.

Sting rating none

ROOT MOUTH

Up to 1m in diameter. Robust with a spherical, solid, rubbery and largely white bell, fringed with purple. The bell lacks tentacles. Doesn't sting.

Sting rating none

COMPASS

Typically up to 30cm, it features 32 marginal lobes and 24 long, thin tentacles. Variable colour. Moderate sting.

Sting rating 2/3

PORTUGUESE MAN-O'-WAR

A floating colony of hydrozoans. Blue-purple with hanging 'fishing polyps' tens of metres long. Rare in the UK. Dangerous due to powerful sting.

Sting rating 3/3