Stalked Jellyfish Bonanza at Mounts Bay

Despite the terrible weather that Cornwall suffered this winter the shore at Marazion was extremely biodiverse for our Shoresearch survey day last Saturday!

A total of 15 volunteers turned out and all were treated to sightings of the nationally rare Stalked jellyfish that are a Feature of conservation interest for this site!  Local naturalists David Fenwick and Dr Paul Gainey joined us in exploring the lower shore shallow eel grass lagoon to the East of the Causeway to St Michaels Mount and straight away we were recording rare stalked jellies.



In total we made:
9 records of Haliclistus octoradiatus -  (5 in the lower shore lagoon and 4 in upper shore pools).
1 record of Leucernariopsis campanulata
1 record of Craterlophus convolvulus 
and 15 records of Leucernariopsis cruxmelitensis

In the past week David has recorded many more Stalked jellies so we now have definite proof that this area is important for these rare protected species. In fact numbers have been so large that it has been described as a bloom! Why this has occurred is not clear and more research needs to be carried out to investigate such rare population explosions.

Maltese Cross Stalked Jellyfish Leucernariopsis cruxmelitensis photo by Matt Slater

Using a hand held GPS Jason Birt was able to record the shore-ward boundary of two large eel grass beds - again a feature of Conservation interest to the site. We discussed with Laurence Smith who runs a stand up paddle board school at Marazion the possibility of returning when the weather is good to map the outer extent of the beds by snorkelling and from paddle boards. It sounds like a great idea - please get in touch if you would be interested in helping out with that!

Long horned porcelain crab magnified! 

Shoresearchers surveying an eel grass filled lagoon

Portrait of a worm pipefish

Generally the level of biodiversity in the site was very high, we recorded lots of Sea hares among the eel grass, and every boulder you looked beneath was home to porcelain crabs, both long horned and broad clawed, Montagues crabs and worm pipefish!

H. octoradiatus by Matt Slater - note the spherical primary tentacles
and the more randomly placed spherical nematocysts

After surveying the lower shore eel grass beds we moved up to a high shore site near the village of Marazion and again found lots of stalked jellys living in pools often attached to wire weed Sargassum muticum. A total of 4 more Haliclistus octoradiatus were found there!

A fantastic day out - and thanks to all of you for turning up!

Looking forward to seeing you over Easter at our next survey on 16th April again at Marazion!

Cheers


Matt