Stand by for jellyfish swarms

There have been far fewer jellyfish sightings so far this year according to the Marine Conservation Society (MCS) which runs the national jellyfish survey.

MCS Biodiversity Programme Manager, Dr Peter Richardson, says there may be a number of reasons why sightings are low: “The incessant rain has meant there have been fewer people out on the beaches or at sea to spot them.

“The unusual meteorological conditions brought about changes to the jet stream which may have also affected jellyfish lifecycles at sea, although at this stage we cannot be sure. Some of our regular jellyfish recorders have told us they have seen fewer jellyfish so far this year.”

However MCS says in the last week the numbers of reports has risen dramatically since the sunny weather and the school holidays started. Dr Richardson says the warmer weather forecast for the rest of the month may well result in more jellyfish blooms in UK waters.

This time last year some parts of UK seas had resembled a jellyfish ‘soup’ when large blooms of thousands of jellyfish were reported. So far this year, most of the sightings have come from the west coast of the UK from the Channel Islands to Argyll and have included barrel, moon and blue jellyfish sightings, whilst large numbers of compass jellyfish were recorded in south west England in late July.

Although UK sightings are down, visitors to the Spain’s Costa del Sol have been warned about massive blooms of Mauve stinger jellyfish. Summer blooms of mauve stingers have plagued the Mediterranean for the last decade, and this year have already left large numbers of people requiring treatment for stings around the coast of Malaga.

Dr Richardson said: “Jellyfish are great opportunists and take advantage if the conditions at sea are favourable to them.

“They are the thermometers of the oceans because jellyfish populations are indicators of the health of our seas. There is now strong evidence that jellyfish blooms are increasing in some parts of the world and this has been linked to overfishing and pollution, while climate change may also be affecting the seas in their favour. The rise of the jellyfish is telling us that we must take better care of our seas.”

The aim of the MCS Jellyfish Survey is to understand more about where and when jellyfish occur around the UK. It’s part of a wider MCS programme to learn about leatherback turtles who migrate thousands of miles to UK waters to feed on their favourite food – jellyfish - each summer.

Over 7,000 jellyfish encounters have been reported since the MCS Survey was launched in 2003 and the survey data is being analysed in collaboration with the University of Exeter. The table below summarises jellyfish reports around the UK this year.

Barrel jellyfish (very mild sting) blooms are largely restricted to the Irish Sea, Solway Firth and the Firth of Clyde, but strays can be recorded further south throughout the year.

Lion’s Mane (powerful sting) are in northern seas, not usually recorded south of the Irish Sea or Norfolk. Found in July in Ayrshire.

Blue (mild sting) Entire UK coast. Found in July in Ayrshire.

Compass (mild sting) Entire UK coast.

Moon (very mild sting) Entire UK coast – most frequently encountered jellyfish in UK waters. Found in January and April in Dumfries & Galloway and in Ayrshire in July.

By The Wind Sailor (very mild sting) An open ocean species, occurs inshore infrequently, but usually in large numbers.

Mauve stinger (powerful sting) Occasionally reported from the Channel Islands & SW England (large blooms off western UK in Autumns of 2007, 2008 and 2009). No reports in UK waters during 2012.

Portuguese Man Of War (dangerous sting) Occasionally recorded, often along SW coast (large numbers reported in late summers of 2007, 2008 and 2009). No reports in UK waters during 2012.

To take part in the jellyfish survey download the full-colour MCS jellyfish photo-ID guide at, where jellyfish encounters can also be reported in detail online.