Wednesday, 25 June 2014

Barrel Jellyfish Bonanza

Barrel Jellyfish bonanza

Giant 20 kilo jellyfish up to one metre in diameter have been making appearances in our waters reports Matt Slater, Marine Awareness Officer with leading local wildlife charity Cornwall Wildlife Trust. Matt along with his famous surfing dog Mango was lucky to have the opportunity to swim with an awesome barrel jellyfish in the Percuil Estuary near St Mawes.

Watch the video at Mango helps to give some excellent perspective on the sheer size of this mesmerising creature!

Many people will have seen these alien looking creatures when on and in the water. This year has been an extremely good year for this species that has been described as the gentle giant of the jellyfish world! And many more jellyfish species have started turning up around our coasts, potentially bringing with them the world’s largest marine turtle!

“It was an otherworldly experience” said Matt Slater of his experience swimming with the giant barrel jellyfish,

“These creatures are incredibly beautiful when you get a close look at them.
The tentacles really look like soft coral, and round the edge of the jellyfish’s umbrella like bell there is a deep blue line punctuated every twenty centimetres or so with a tiny dot, a sensory statocyst. Jellies are more aware of the watery world around them than you may imagine. They are constantly swimming up and down in the water column looking for profitable patches of plankton. The statocysts are their sensory cells that enable them to orientate and tell up from down.”

Like a basking shark, barrel jellies feed exclusively on plankton which is caught with sticky mucous covered tentacles, and like a basking shark they are fortunately totally harmless to humans, their stings being too weak to get through human skin.

Matt Slater continues,
Lots of people have been calling Cornwall Wildlife Trust to ask us why there are so many jellies this year. In the spring tiny anemone like jellyfish ‘polyps’ living on the sea bed expand in size and then bud off thousands of tiny larvae. Most years these larvae will perish but in years where the conditions are good, temperatures are optimal, there is plenty of planktonic food and predators do not eat them all, large numbers of them will survive creating these huge jellyfish swarms. It is a boom and bust cycle. In fact according to our records the last time such large numbers of Barrel jellyfish were seen in Cornwall was in 2002.”

On Cornwall’s north coast huge numbers of blue jellyfish have been found. Last night Matt and his fellow members of Holywell Bay Surf Club paddled through a swarm containing hundreds of these blue stingers, between Holywell and Perranporth. Unlike barrel jellies blue jellies can give a mild sting so please take care around them if you find any. Matt reported “We also saw compass jellies and moon jellies last night so jelly season is officially here!”

One of the most exciting things about this news is that where there are jellyfish there is a greater chance of seeing their predators. Two sightings of leatherback turtles have already come into Cornwall Wildlife Trust this summer, one off Porthcurno and one in Falmouth Bay. The leatherback turtle is a prehistoric looking creature, the largest marine turtle species, growing to up to eight foot long. It ventures north into Cornish waters in the summer months to feed on jellies!

We urge the public to get in touch and record their sightings of marine animals. This information is incredibly useful and appreciated. To submit a record please use our user friendly website,

Cornwall Wildlife Trust work to protect Cornwall’s wildlife and wild places. There are many ways you can get involved visit for more information. 

Wednesday, 18 June 2014

Stand up Paddle Board reccie of Marazion eel grass beds with Ocean High

I was privileged to have the opportunity yesterday to try out a totally new method of marine surveying. Laurence Smith of Ocean High, Marazion took me on a Stand Up Paddle board (SUP) exploration of the shallow lagoon to the East of the St Michael's Mount Causeway. This is a terrific method of exploring the shallow waters  and we are hoping to go back to accurately map the eel grass beds found there.
From the high vantage point of a SUP board you can see down into the water and on a clear day like this one it meant we had a fantastic view as we glided over the surface. A video camera mounted beneath Loz'z board allowed us to capture video as we traveled. A GPS was used to record the position of the outer edges of the eel grass beds in this site.

It was a fantastic survey and we now know that a SUP is a good platform for this kind of work. As the wind started to pick up and ruffle the surface of the water I got in and snorkeled and was able to ground truth our survey area. Interestingly we found what appears to be evidence of storm damage sustained by the eel grass this winter. In many areas you can see exposed rhizomes from the eel grass and a clear step is evident where sand has been removed probably taking with it eel grass plants themselves.

Damage where the sand has been removed by storms - root like rhizomes are now exposed at the edge of the remaining eel grass rhizome matt. 

Healthy eel grass Zostera marina.

Loz and the Mount 

Hairy sand weed looking like coral - Cladostephus spongiosus

Leucernaryopsis cruxmelitensis Stalked jelly fish found on Ulva lactuca sea lettuce

A SUPs eye view of the lagoon - note large rainbow wrack plants, Sargassum muticum and Bifurcaria bifurcata in foreground. 

Juvenile ballan wrasse - bright green to help them camoflague against the eel grass and sea lettuce

Sunday, 15 June 2014

Battery Rocks ROCKS

We had a great turnout of volunteers for the Shoresearch survey today at Battery Rocks right next to the jubilee pool, Penzance. My good friend Rory Goodall of was leading a fox club rockpooling event and myself and the Shoresearch volunteer team came along to conduct a survey of this important site! We were not disappointed! It is a fantastic shore!  We were met by David Fenwick of who showed us no end of fascinating tiny creatures we wouldn't have found otherwise! I definitely need a set of reading glasses! It was great to meet Liam from Falmouth aquarium and his girlfriends dad and brother who relentlessly discovered interesting things.
Prize for find of the day was definitely the candy striped flatworm and the beautiful Risso's crab found by Rob wells who had travelled all the way from Mevagissey to be at the survey (Margaret and Tim came even further, travelling all the way from Fowey!)
I'm looking forward to heading to Mounts bay again soon - next survey / public event is at Long Rock on the 12th July!

In this gully there is a multitude of seaweed species

Cowrie grazing in a lowershore overhang

Thanks to David Fenwick for helping us find this bizzare tiny isopod Campecopea hirsuta that lives inside empty barnacles on the upper shore at this site. this one was about 3mm. You are looking at its abdomen and the spine that is sticking up is part of pereon segment 6 of its back.

Montagues blenny portrait! Ruben found 10 of these in one pool.

Rissos crab Xantho pilipes found by Rob Wells

Hairy legs are the key identification feature but they are also far more colourful than Montagu's crabs.

David found this piece of rock covered in sponge and barnacles Acaster spongites within Dysidia fragilis sponge.

I found  this just sitting on a muddy ledge inside a small cave out of the water - a topknot - a type of flatfish.
Rob Wells found this beautiful large (one inch) candystripe flatworm.
Gastroclonium ovatum - Red grape weed