World Jellyfish Day: Some of the jellyfish superstars you can spot on UK shores

By: Victoria Riglen
Date posted: 2 November 2020

Today marks World Jellyfish Day, and we’re not ones to turn down an opportunity to talk about jellies! We’ve rounded up some of the jellyfish you’re most likely to spot on the UK coastline and share how you can get involved in our Jellyfish Survey.

Compass Jellyfish - Abercastle
© Paul Naylor

The weather will be blowing them in from the Atlantic as part of another major Portuguese Man of War stranding event - the last one was in similar conditions in 2017 and they seem to be getting more frequent since we started our survey in 2003.

Dr Peter Richardson,
Head of Ocean Recovery

To date, thousands of people have shared sightings of jellyfish from around the UK, helping to build an extensive data set of six jellyfish and two jellyfish-like hydrozoan species. Understanding trends in jellyfish distribution and numbers can help us understand where leatherback turtle feeding grounds might be, as well as potentially indicating the impacts of climate change on our ocean. Most adult jellyfish have died off in the UK autumn months, but some species, including the Portuguese Man ‘o War are still around – so watch out when you are on the beach this month….

Aurelia aurita aka Moon

Recognisable thanks to the four pale purple rings on its bell, these jellyfish can grow up to 40cm in diameter. The bell is transparent and umbrella shaped with short, hair-like tentacles. Amongst the hair like tentacles you’ll spot four short, frilled ‘arms’. The Moon jellyfish has a very mild sting, so no need to panic.

Moon Jellyfish

Chrysaora hysoscella aka Compass

Look, but don’t touch…this jellyfish stings. Typically growing up to 30cm in diameter, the compass varies in colour but typically has a pale, umbrella-shaped bell, with brownish v-shaped markings. Amongst the compass’ 24 long and thin tentacles are four longer, thick, frilled arms.

Compass Jellyfish - Abercastle

Cyanea capillata aka Lion’s mane

Social distance from this one, this jellyfish has a very painful sting. One of the larger jellies you can spot in UK waters, although mostly confined to more northerly waters, lion’s mane jellyfish are usually 50cm in diameter, but can reach up to two metres across. Recognisable from its reddish brown umbrella shaped bell, a shaggy ‘mane’ of red hair-like tentacles, as well as a fringe of many-metres-long thin stinging tentacles that promise plenty of pain – not to be messed with!

Lion's mane jellyfish

Cyanea lamarckii aka Blue

With a similar shape to the Lion’s mane, but with a distinctive colouring, the blue jellyfish is much smaller, growing up to 30cm in size. The blue jellyfish has a smaller, blue bell through which you can see line markings. Confusingly, the blue jellyfish also comes in yellow! This jelly has a mild sting, so as always, approach with caution.

Blue jellyfish

Rhizostoma pulmo (formerly octopus) aka Barrel

This is the Arnold Schwarzenegger of jellyfish, growing up to one metre in diameter, weighing up to 30 kgs and sporting a solid, spherical, rubbery looking bell which can be white, pale pink, blue or yellow. The bell doesn’t have any tentacles but eight thick, frilled arms hang down – hence its former scientific name octopus. The barrel jellyfish also has a mild sting.

Barrel Jellyfish

Pelagia noctiluca aka Mauve stinger

As the name suggests, this jellyfish stings, and it really hurts, so please don’t touch. Much smaller than most of the other jellyfish in this list, the mauve stinger grows up to just 10cm. The bell of this jelly is covered in pink or mauve warts and has eight hair like tentacles alongside four longer frilled arms with tiny pink spots.

Mauve stinger

And, whilst technically not a jellyfish…

Physalia physalis aka Portugese Man o’War

Whilst this creature bears some resemblance to jellyfish, the Portugese Man o’War is in fact a floating colony of hydrozoans. Look out for an oval shaped, transparent float which is blue/purple in colour. Below the oval float hang ‘fishing polyps’ that can be tens of metres long and can be dangerous to humans due to their powerful sting. These are usually relatively rare in the UK but are washing up in large numbers this autumn along the South West coast.

Stranded Portuguese Man of War

Dr Peter Richardson, Head of Ocean Recovery: “Through our online jellyfish survey, we’ve been receiving reports of Portuguese Man of War on beaches in south Wales in September. Through October we’ve continued to receive reports of them appearing on beaches in Devon and Cornwall, with mass strandings in Cornwall this weekend. The weather will be blowing them in from the Atlantic as part of another major Portuguese Man of War stranding event - the last one was in similar conditions in 2017 and they seem to be getting more frequent since we started our survey in 2003.”

“We urge beachgoers not to touch them…they pack a very powerful sting! But, please do report them on our website so we can better understand the extent of this stranding event.”

For more information on the most commonly spotted jellyfish around the UK, please consult our Jellyfish ID Guide. To report a jellyfish sighting, follow this link.

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