Jellyfish in UK Seas

Jellyfish in UK Seas

When the sea water gets warmer in summer it causes blooms of jellyfish in UK seas. Have you seen them washed up onto the beach?

A few years ago the Marine Conservation Society (MCS) and the University of Exeter published a report of where and when UK jellyfish occur in UK seas. It was the first one for over 40 years and was published in the Journal of the Marine Biological Association.

Details were included of over 5000 reports of jellyfish sightings of eight different species. They were sent in by the British beach going public between 2003 and 2011 for the MCS National Jellyfish Survey. More than 3,500 jelly-spotting volunteers sent in their sightings. Dr Richardson from MCS says “Our paper shows that publicly driven, collective citizen-science can help us understand our environment on a scale that would otherwise be unaffordable.”

Dr Richardson added, “We still know relatively little about jellyfish, but given the economic impacts that large numbers of jellyfish can have on tourism, fishing, aquaculture and even power generation, we can’t afford to ignore them.”

Recording Sightings of Jellyfish in UK Seas

The survey is the largest of its kind on jellyfish in UK seas and has attracted lots of jellyfish sightings. 2013 was a record year when 1,133 reports were received. If you’ve been on a beach in the summer of 2018 you’ll know that they’ve done well this year too.

It’s not just interesting information. By taking stock of jellyfish in UK seas in this way, it provides important information which helps us to understand how jellyfish species react to environmental changes that influence our coastal seas, including climate change.

The top five jellyfish species in the report are:

  • Moon – 29% of recordings, found all around the UK from May to September
  • Compass – 19% of recordings, with a southern distribution (Merseyside to Norfolk), from June to October
  • Lion’s mane – 18% of recordings, have a northerly distribution (North Wales to Sunderland), found from May to October.
  • Blue – 15% of recordings are usually found in SW England and Wales, NE England and Scotland. From May to September.
  • Barrel – 10% of recordings. Hotspots in Welsh and Scottish waters and they’re reported throughout the year.

The other species of jellyfish in UK seas are the mauve stinger, Portuguese Man of War (which is a close relative of jellyfish) and the by the wind sailor (also a close relative of jellyfish). Together they make up approximately 10% of survey records but aren’t recorded every year.

Register your Sightings of Jellyfish in UK Seas

Taking part in the jellyfish survey is fun and easy!

Look carefully at them before reporting, but remember not touch jellyfish found in UK seas as some species have a powerful sting.

More about Jellyfish in UK Seas

The moon jellyfish – below (Aurelia aurita) is the most widespread species, occurring all around the UK coast from May. So does the less common blue jellyfish (Cyanea lamarkii).

Moon jellyfish on the beach, jellyfish in UK seas
Moon Jellyfish – this one looks like it’s been out of the sea for some time…

The giant but harmless barrel jellyfish (Rhizostoma octopus) can grow up to 1 metre in diameter and weigh up to 40kg. It’s largely limited to the Irish Sea and nearby waters to the north. It occurs year round, even in winter, but blooms of these jellyfish in UK seas tend to start in March.

The lion’s mane jellyfish – below (Cyanea capillata) has the most powerful and painful sting of the UK jellyfish. It blooms during the summer but is rarely seen south of the Irish Sea (west coast), or south of Northumberland (east coast). Most reports come from Scottish waters.

Lions Mane jellyfish on the beach, jellyfish in UK seas
Lions Mane Jellyfish

The compass jellyfish (Chrysaora hysoscella), has bizarre compass-like markings. It’s one of the jellyfish in UK seas found around all the coast.

Mauve stingers (Pelagia noctiluca) are occasionally recorded from the southwest in early spring. Large numbers were reported off Britain’s west coast during November 2007, 2008 & 2009.

Similar – but not actually Jellyfish…

MCS also received many reports of the usually rare Portuguese Man-of-War (Physalia physalia) from beaches in south-west England in the summers of 2007, 2008 and 2009.

Sea gooseberries – below, are often seen washed up on the beach. These comb jellies look like tiny little jellyfish, but they’re actually totally unrelated. Despite their delicate, almost ghostly appearance, sea-gooseberries are voracious predators. They feed on fish eggs and larvae, molluscs, copepod crustaceans, and even other sea-gooseberries.

Sea gooseberries on the beach, jellyfish in UK seas
Sea gooseberries on the beach
Sea gooseberries on the beach, jellyfish in UK seas
Sea gooseberry

The data on jellyfish in UK seas was analysed in collaboration with the University of Exeter’s Centre for Ecology and Conservation. It’s a state-of-the-art facility near Falmouth and part of the internationally recognised School of Biosciences.

Have you got any photos of jellyfish that you’ve spotted off the Fylde Coast? If you have please send them in.

Find out More

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