"Overnight in Y Llanfa, Aberystwyth.... Calm seas but no Cataceans.... lots of Rhisostoma Octopus (Barrel) Jellyfish in the clear waters between Llanrhystud and Aberystwyth" excerpt from Dan Worth Facebook message.
Rhisostoma or Barrel Jellyfish are the main food for the elusive Leatherback Turtle. I first remember being amazed at seeing some really big Rhisostoma's in the Celtic Deep in March some years ago. At one time we saw quite a few regularly off the ferry particularly around Rosslare Harbour although this has ceased to be so in the last two or three years. all the same they seem to be just as common in Cardigan Bay these days. It seems likely these big jelly fish are not just swept along on tides but may be capable of navigating to some degree. Either way it would be interesting to know a bit more about their seasonality which in turn might help us to understand more about Leatherbacks.