Compass Jellyfish – Info & Identification

Compass Jellyfish – Info & Identification

Seasonal visitors

This year I spotted my first Compass Jellyfish at the start of June, and by mid-July they were everywhere in Cornwall’s waters. I observed them all along the coast from the Fal down to the Lizard Peninsula, often in big numbers. Interestingly, they appeared almost at the exact same time that the Blue Jellyfish disappeared. For several weeks they were abundant, but by mid-August I hadn’t seen a single one. Like many jellyfish species, they come and go with the seasons. Once they were here they far exceeded the smack of Blue jellies we say earlier in the season. This is probably due to a mild winter and a particularly warm summer.

How to identify them

Compass Jellyfish are easy to recognise thanks to the brown markings radiating symmetrically from the centre of their bell - almost like a compass. They have a delicate frilled edge and long, thin tentacles, which can be difficult to see in cloudy water but glint in the sunlight. They are active predators, feeding on plankton, small fish, and pretty much anything they can catch.

Safety and behaviour

Their sting is stronger than the Blue Jellyfish, and can still pack a punch even if the animal is washed up dead. It’s often compared to a wasp or bee sting - painful, but not dangerous. I always make sure to spot the full trail of their tentacles before moving in to take photos, approaching from up-tide so they drift away. Unlike some species, Compass Jellies seem aware of divers and will pulse away when you get too close, good for summer sea swimmers. Although there are lots, the likelihood of unknowingly swimming into one is low. If you like to see some videos of compass jellies, head to my Instagram on the link below.