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Published - 21/07/2011

HUGE NUMBERS OF JELLYFISH SWARM IN UK'S SUMMER SEAS 

MCS urges beach goers and sea users to take part in a national survey as barrel, moon, compass, blue and lion's mane jellyfish swarm in our seas.  

Fascinating to some and frightening to most, jellyfish numbers appear to be on the increase in UK seas, with the recent shut down of Scotland's Torness nuclear power station directly due to swarms of moon jellyfish blocking the water intake cooling systems. As the UK's seas continue to warm up over the summer, more jellyfish blooms are expected, and as the nation prepares for the summer holidays, MCS is urging beach goers and sea users to take part in their national jellyfish survey. 

"The jellyfish survey is an excellent way for people to get involved in finding out more about our threatened seas. There is strong evidence that jellyfish numbers are increasing around the world, including UK seas, and these increases have been linked to factors such as pollution, over-fishing and possibly climate change," says MCS's Peter Richardson. "We should consider jellyfish populations as important indicators of the state of our seas, and the MCS jellyfish survey helps provide some of the information we need to understand more about them." 

Taking part in the jellyfish survey is easy! The full-colour MCS jellyfish photo-ID guide can be downloaded and jellyfish encounters can also be reported in detail online here.

Already, some areas of the UK's seas resemble a 'jellyfish soup', such as the Irish Sea where large numbers of moon, lion's mane, blue and compass jellyfish have already been reported. 

"Most jellyfish bloom in summer, but some species can survive the cool winter months too," says MCS Biodiversity Programme Manager Peter Richardson, "This year, we received our first reports of the huge but harmless barrel jellyfish off North Wales back in early January, and this species has occurred in huge numbers in the Irish Sea and beyond ever since, with reports received from North Somerset to the Firth of Clyde. Since May we have also received reports of large numbers of several other species of jellyfish from various coastal all sites round the UK - it is another good year for the jellyfish!"  

MCS aims to understand more about where and when jellyfish occur around the UK though their survey. While encouraging beach lovers and coastline visitors to report their findings, MCS also warns to 'look but not touch' as some jellyfish can sting - particularly the lion's mane that is swarming in huge numbers at some coastal sites in the north west. 

Jellyfish are the staple diet of critically endangered leatherback turtles, seasonal visitors to UK seas, which migrate from their tropical nesting beaches to feed on our abundant seasonal jellyfish blooms. Examinations of dead leatherbacks stranded on UK shores have revealed that they feed on several species of British jellyfish. By comparing the distribution of jellyfish with environmental factors such as sea temperature, plankton production and current flow, we hope to understand what influences the seasonal distribution of jellyfish and leatherbacks in UK waters. This year there have been three confirmed leatherback sightings since June, all spotted in waters off western UK where jellyfish blooms have been reported. 

Over 6000 jellyfish encounters have been reported since the MCS Survey was launched in 2003. The survey data is being analysed in collaboration with the University of Exeter and early results of the public sightings show interesting differences in the distribution of the larger jellyfish species around Britain. 

 

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