How to spot jellyfish in UK and what to do if you’re stung

One of the greatest challenges facing ocean campaigner Lewis Pugh in his quest to swim the length of the English Channel is the sheer number jellyfish that he’s encountered.

In recent weeks, he’s been stung so many times that it’s made his 350-mile swim much harder.

The increase in jellyfish blooms is being put down to climate change and extreme weather conditions, from the bitterly cold temperatures we saw in March to the scorching hot summer. Others believe overfishing of jellyfish predators doesn’t help.

Jellyfish are particularly prevalent in Scotland and along the South Coast, where Lewis is carrying out his swim. He now has a designated jellyfish spotter on board to guide him away from them so that he’s not stung quite so often.

Dr Cathy Lucas, associate professor in Marine Biology at the University of Southampton, explains how to spot the UK’s species of jellyfish and what to do if you are stung.

The UK has six species of true jellyfish and two species of jellyfish-like animals, the Portuguese man o’war and by-the-wind-sailor, which are both classified as siphonophores.

Jellyfish are most likely to be seen from mid-spring through to late summer and early autumn, depending on species and also the weather and oceanographic conditions. None of the UK jellyfish are considered to be dangerous, although a couple do have fairly nasty stings.

In the UK, the Marine Conservation Society (MCS) manages a public sightings scheme through which the public can report sightings and stranding data for all the UK jellyfish species.

Common or Moon jellyfish (aurelia aurita)

Easily recognised by its four horseshoe-shaped gonads on the top of its bell, the common jellyfish is found in all UK waters, particularly in marinas, estuaries and bays.

Aurelia aurita is the most commonly sighted species, typically seen from mid spring through to mid summer. Common jellyfish can grow up to 30-40cm in diameter and are mostly transparent, except for pale pink to orange tentacles and gonads.

Their sting is extremely mild.

Compass jellyfish (chrysaora hysoscella)

Compass jellyfish are characterised by V-shaped brown stripes radiating out from the centre of the bell, much like the points of a compass.

They are up to 30cm in size and have 24 long thin tentacles and four frilled “arms” hanging underneath. The compass jellyfish are found mainly in the southern half of the UK during the summer months.

Although not dangerous, their sting can be quite painful.

Blue jellyfish (cyanea lamarckii)

This jellyfish is typically a bright blue/purple colour but there are also brown morphs. It has a scalloped edge and long, fine tentacle trailing underneath.

It is common in the South West and Wales during the late spring to summer months, but can also be seen along the North Sea coastline.

It has a mild sting.

Lion’s mane jellyfish (cyanea capillata)

The lion’s mane is a relative of the blue jellyfish. It prefers colder waters, so it is found mainly from North Wales, right up to the north of Scotland and beyond.

The scalloped-edged bell is reddish-brown in colour and can range in size from 30cm up to two metres in diameter. A mass of very fine tentacles trail for up to 10-20 metres and these have a nasty sting.

Swimmers, divers and snorkelers may find they get stung by the barely visible tentacles if they have broken off from the animal.

Barrel jellyfish (rhizostoma octopus)

The barrel jellyfish has a very distinctive solid, rubbery bell up to one metre in diameter. Its colour varies from pale pink, cream or brown fringed with purple markings around the edge.

This jellyfish does not have tentacles; instead eight thick, frilled arms that look a bit like cauliflower florets hanging underneath.

Although very large, this jellyfish is harmless and has only a very mild sting.

Barrel jellyfish are less common, being found mainly along the coastlines of the South West, Ireland, Wales and western Scotland, either in more open water or washed up on beaches in the summer and autumn months. It is thought to live year round.

Mauve stinger (pelagia noctiluca)

The mauve stinger is common in the Mediterranean during the summer and due to its nasty sting, it can cause problems for beach tourism.

It is relatively small (10cm) and is characterised by a more conical shape covered in pink or mauve warts. Four long frilled arms hang underneath.

It is rare in the UK and only found along the south coast in warm summers.

Portuguese man o’ war (physalia physalis)

The characteristic purple-blue oval-shaped float with “tentacles” hanging for up to tens of metres underneath is familiar to many people.

It is not a jellyfish; instead a colony of hydrozoans. It lives in the open ocean floating at the surface.

If gales blow in from the Atlantic Ocean in the late summer and autumn, several may get washed up along the South Coast, although this does not happen every year.

The Portuguese man o’war is the most dangerous of our jellyfish and jellyfish like animals as they have a powerful sting.

By-the-wind-sailor (velella velella)

Like the Portuguese man o’war, this is not a true jellyfish.

Velella is blue in colour and has a very distinctive triangular sail on top of a circular base under which hang small tentacle. It floats on the surface of the sea and is blown by the wind.

It can occur in vast swarms and if there are strong westerly and south-westerly winds blowing in from the Atlantic Ocean in the late summer and autumn months, huge numbers are stranded along the South West and Welsh coastlines, although this is rare.

They are harmless.

Advice on stings

If jellyfish are seen in the water or on the beach, the general advice is not to touch them.

If people do get stung, any tentacles attached to the skin should be removed and the area washed with salt or fresh water.

Jellyfish species in the UK are not dangerous, although stings from the Portuguese man o’war, Lion’s mane and Compass jellyfish can be painful and those who have allergic reactions to stings should monitor the sting and seek medical attention if necessary.

(c) Sky News 2018: How to spot jellyfish in UK and what to do if you’re stung