UK Freshwater Jellyfish

Have You Seen a Freshwater Jellyfish in the UK?

Most people know jellyfish are in the ocean, however jellyfish can also be found in freshwater bodies like ponds and lakes. The freshwater jellyfish, Craspedacusta sowerbii, was first described in London in 1880, but has been reported only a few times in the United Kingdom since. This elusive non-native freshwater jellyfish is likely more widespread across the UK than is currently recorded, so your sightings could help us to better understand this widely overlooked species. A research team based at the University of Plymouth is seeking observations of freshwater jellyfish anywhere in the UK and you can help by letting us know when and where you see them!

This small jellyfish (~2.5cm) can be found in still water bodies, like ponds, lakes, canals, reservoirs, etc. It typically appears irregularly between June and September, when the water temperature exceeds 21 C, so is hard to spot. Please let us know:

When you saw them (date and time) - even if you saw them in previous years!
Where you saw the freshwater jellyfish (location and/or geographical coordinates).
How many freshwater jellyfish did you see? (1, <10, 10-100, 100-500, 500-1000, more than 1000) 

We’d be very grateful if you could also provide a photograph or a video of your sighting! If you are comfortable catching freshwater jellyfish and can do so without putting yourself in any danger, please put a couple in a jar and contact us soon. Catching freshwater jellyfish could be an important way to help us learn more about them.

Since the first taxonomic description of C. sowerbii in London in 1880, research has shown there are at least three distinct genetic lineages of C. sowerbii globally. It is likely that a number of potentially different species have previously been lumped into the category of C. sowerbii, so the exact lineage of C. sowerbii is uncertain. This uncertainty makes it important to collect specimens and investigate the genetic lineage(s) present in the United Kingdom, in order to potentially stabilise the nomenclature. This investigation will provide the basis for future research into the global spread of this non-native cryptic species.

Please connect with us here. Include time/date when you observed freshwater jellyfish, location where you saw them (name of waterbody, location name, or coordinates), and how many freshwater jellyfish you saw. You can also attach photos and videos (or links to videos) to your email. Thank you very much for your observation!