Survey of jellyfish may help save rare turtle

Click to follow
The Independent Online

Do not think of them as wobbly. Do not think of them as menacing. Think of jellyfish as fascinating, and make a note whenever you see one, marine scientists say today. Seaside visitors are being asked to take part in a mass survey of jellyfish around the coast this summer, to shed light on the habits and life cycles of some of the ocean's most enigmatic creatures.

Jellyfish are marine animals related to sea anemones and corals. They typically have a gelatinous umbrella-shaped body with trailing tentacles.

"Everybody's familiar with them, yet we know hardly anything about them," said Peter Richardson of the Marine Conservation Society (MCS), which is organising the survey.

The MCS also warns people to take care when they find potentially dangerous species. Half of the jellyfish found in British waters can sting, and some, including the lion's mane jellyfish, can sting badly enough to put people in hospital. The Portuguese man-of-war can be fatal, but those creatures are rare on our coasts.

To avoid accidents, the MCS is distributing a free full-colour guide to Britain's eight commonest jellyfish species. Some, such as the moon jellyfish, will be familiar; others, such as the mauve stinger, will be less well-known. The society is warning people to use a stick or wear rubber gloves if they turn a jellyfish over for identification.

Behind the survey lies the threat to another fascinating sea creature, the leatherback turtle. The leatherback, which is critically endangered, is the only one of the seven marine turtle species that frequents British waters, and it feeds almost exclusively on jellyfish.

The MCS wants to investigate the relationship between jellyfish distribution around the UK and the seasonal appearances of the leatherbacks. If the survey shows up seasonal hot spots for different jellyfish species, that may help target turtle conservation measures, such as warning the fishermen in whose gear they often drown.

The MCS says there are plenty of jellyfish. In the past few weeks, vast blooms of the harmless moon jellyfish Aurelia aurita have been reported off north Devon, west Wales and the north-west coast of Scotland. A few of the beautiful blue Cyanea lamarckii and compass Chrysaora hysoscella jellyfish have appeared off Devon and Cornwall, and thousands of massive barrel jellyfish, Rhizostoma octopus, have been recorded in the Irish Sea, and stranded in vast numbers on Welsh beaches. But swarms of the giant lion's mane jellyfish Cyanea capillata are appearing off north-west England and Scotland. Britain's largest jellyfish species, the lion's mane, can reach up to two metres across, and last year unsuspecting bathers who hit dense swarms of the jellyfish in the Mersey estuary suffered severe and painful stings. MCS also had reports of swimmers being stung off Anglesey and the west coast of Scotland.

"Jellyfish will not purposely attack people," Mr Richardson said. "They catch fish and other marine creatures by spreading their tentacles like fishing lines. The tentacles of some species can inflict painful stings, especially those of the lion's mane jellyfish. The other species most commonly found in UK waters are either harmless or inflict mild stings, but you never know how an individual will react to the venom."

* The identification guide and survey form can be obtained from the Marine Conservation Society, Unit 3, Wolf Business Park, Ross-on-Wye, HR9 5NB. Telephone 01989 566017 or e-mail

A guide to safe spotting

Moon jellyfish Aurelia aurita: Most people will be familiar with this British species, recognised by four distinct pale-purple rings (gonads) inside the transparent bell. Grows to 40cm across and has a mild sting.

Lion's mane jellyfish Cyanea capillata: This has an easil recognised large, brown, umbrella-shaped bell, which has a mass of long, hair-like tentacles. Can grow to reach two metres across. Classed as dangerous.

Compass jellyfish Chrysaora hysoscella: Pale, umbrella-shaped bell, with brownish v-markings. Four frilled arms are 30cm across. Do not touch.

Blue jellyfish Cyanea lamarckii: Similar in shape to lion's mane but smaller, with a blue bell through which radial line can be seen. Up to 30cm across. Mild sting.

Barrel jellyfish Rhizostoma octopus: A spherical, solid, rubbery and largely white bell, under which eight thick, frilled arms hang down. Grows to a metre across.

Mauve stinger Pelagia noctiluca: Small jellyfish with a deep bell with pink or mauve warts, and four hanging, frilled arms with pink spots. About 10cm across. Do not touch.

By-the-wind-sailor Velella velella: Not strictly a jellyfish but a similar marine animal called a hydranth. Blue-purple, up to 10cm long with an upright 'sail'. Usually found in vast swarms.

Portuguese man-of-war Physalia physalia: Actually, a floating colony of hydrozoans. Blue-purple, with an oval transparent 'float' and long stinging tentacles. Very dangerous.