SIGHTINGS of ‘massive’ barrel jellyfish have reached record levels for a second consecutive year, according to a leading marine charity.

The Marine Conservation Society (MCS) says the rise “can no longer be ignored” and is calling for more research to understand the apparent increase.

Although barrel jellyfish are reported all around the UK, the majority are spotted in the south west and south of England. Last year 1,400 sightings of jellyfish were reported and this year is set to be another bumper year. So far in 2015, 75 per cent of records have been barrel jellyfish, and August is a peak month for sightings.

The species of jellyfish most commonly spotted off Dorset are barrel, moon, compass and blue.

Barrel jellyfish

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Barrel jellyfish can grow to the size of dustbin lids and are very rubbery and robust. When the weather warms up they rise to the surface to feed on the plankton and to breed.

They are generally harmless in spite of their size. All jellyfish can sting but theirs is thought to be very weak.

The giant jellyfish can grow up to 90cm (35in) wide and weigh as much as 25kg (55lb), while their tentacles can reach lengths of 6ft (1.9m). 

Compass jellyfish

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Picture sent in by Kimberley Hall

Compass jellyfish can grow more than three meters of stinging tentacles and have turned up in 'reasonable numbers' off Dorset. 

The venom in the stinging cells is very strong and can produce painful, long lasting welts in humans.

The Compass jellyfish started to appear in June, with most reports in July from South West England, South West Wales and North West England. 

Blue jellyfish

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Credit Peter Richardson/MCS

Blue jellyfish get their name from their distinctive colour.  They do sting and symptoms can include intense hurtful pain, welts, and a rash while in extreme cases it can cause vomiting, fever, sweating, chills, swelling of the lymph nodes, back and abdominal pain.

They started to appear in May and by July were reported all around the UK. 

Moon jellyfish

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Picture by Marine Conservation Society 

Also known as Common and Saucer jelly, the Moon jellyfish do not sting humans. The threadlike tentacles around the edge of the bell can sting, and may occasionally catch small swimming animals for food, but their stings are not powerful enough to penetrate human skin. The moon jellyfish glow orange when full of plankton. They are found in the Atlantic, Pacific and Indian oceans.

Dr Peter Richardson, MCS biodiversity and fisheries programme manager, said: “We know that our seas are changing through climate change, resulting in rising sea temperatures and increased ocean acidification, and we know our seas are also heavily fished.

“At the same time we seem to be witnessing increases in jellyfish around the UK. Is this an anomaly, a coincidence, or are the jellyfish telling us something about fundamental changes in the condition of our seas?”

As well as the high number of barrel jellyfish, there were reports of mauve stingers and the potentially deadly Portuguese man-of-war along the south coast.

A group of jellyfish – known as ‘smacks’ – are not a new phenomenon, with jellyfish blooms having been found in the fossil record over 500 million years.

In recent times they have had important economic and social consequences. Moon jellyfish blooms have forced the closure of UK nuclear power stations, leading to the industry investing in remote sensing mechanisms to detect increases in jellyfish near power plants.

Large blooms of mauve stinger jellyfish have also wiped out salmon stocks in fish farms in the UK, while the same species regularly closes down bathing beaches in the Mediterranean due to the animal’s painful sting.

“People are fascinated by jellyfish and that’s why our survey is one of our most successful citizen-science projects,”added Dr Richardson. 

“But we believe there is now a need for UK government to commission dedicated scientific research and monitoring to answer pressing questions about what is happening to jellyfish numbers, why it is happening and what this means for our precious and productive seas.”

MCS is now urging the public to report their jellyfish sightings online at www.mcsuk.org but urges caution, suggesting people look at but do not touch jellyfish because their stings can range from mild to very painful.