A new report by the Marine Conservation Society (MCS) and the University of Exeter takes stock of where and when UK jellyfish occur in UK seas for the first time in over 40 years.

The report, published in the Journal of the Marine Biological Association, details over 5000 reports of jellyfish sightings of eight different species sent to MCS by the British beach going public between 2003 and 2011 for their MCS National Jellyfish Survey.

The survey is the largest of its kind in the UK and has been attracting a growing number of jellyfish sightings, with 2013 proving a record year when 1,133 reports were received. This year is also turning out to be good for jellyfish, with over 500 reports already received by mid-July, only halfway through summer months when most records are received.

“Our survey puts jellyfish on the map in the UK. In this latest paper we show where and when these species now occur throughout UK coastal waters,” said Dr Peter Richardson, Biodiversity Programme Manager for the MCS, “The last time the national picture was described was well over four decades ago, so this study provides a very timely update.”

Prof. Brendan Godley of the University of Exeter said, “By taking stock of our jellyfish in this way, we provide an important baseline of information which will help us understand how jellyfish species react to environmental changes that influence our coastal seas, including climate change.”

The top five jellyfish species described in the report are summarised below.

The survey depends on the generous support of an army of over 3,500 jelly-spotting volunteers, who have been diligently sending in their sightings throughout the year every year since 2003. Dr Richardson says “Our paper shows that publicly driven, collective citizen-science can help us understand our environment on a scale that would otherwise be unaffordable.”The other species are the mauve stinger, Portuguese Man of War (close relative of jellyfish) and the by the wind sailor (also a close relative of jellyfish), which together make up approximately 10% of survey records and are not recorded every year.

This year MCS has so far received reports of seven of the eight species, including barrel, moon, blue, compass, lion’s mane, mauve stingers and by the wind sailors from around the UK. As the summer progresses we can expect to see many more jellyfish reported to the MCS survey, and so far barrel jellyfish have made up the majority of reports, with most of these reported from South West England and Wales.

“The remarkable number of barrel jellyfish reported from South West England this year is quite unusual, and at odds with what our report describes, previous years have seen hotspots for this species in West Welsh and Scottish waters,” said Prof. Godley, “We’re not sure why, but the very mild winter probably meant more adults survived at depth, which will have returned to the surface in spring as waters warmed up. This year’s strange barrel jellyfish results highlight the importance of running the survey year in and year out to track these unusual events and discover if they turn into trends”.

Dr Richardson said, “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.”

Taking part in the jellyfish survey is fun and easy. The full-colour MCS jellyfish photo-ID guide can be downloaded from www.mcsuk.org, where jellyfish encounters can also be reported in detail online. Survey participants should always remember to look carefully at jellyfish before reporting them, but should not touch them as some species have a powerful sting.