If you've walked on a beach this summer or stood on a pier looking into the ocean, chances are that you will have seen them....
As an ORCA Wildlife Officer I use them as a tool to get children interested before a ship has even left harbour. They float mysteriously below the side of the ferry in a plethora of shapes and colours: an exotic and magical creature hinting at the strange and wonderful world that exists beneath the waves. They are jellyfish. And in recent years we have seen huge numbers of these incredible invertebrates in our waters. Every summer, a different sensational round of news stories emerges about them; whether it is an invasion of them on our beaches, or the dangers of being stung by jellyfish. This year it was the gigantic size of a barrel jellyfish that wildlife presenter and recent ORCA Sea Safari guest Lizzie Daly was photographed scuba diving next to in Cornwall. The jelly was so large that it dwarfed her and her fellow diver!
Actually these creatures are nothing new and have populated our oceans for millions of years. A seemingly basic but really rather complex life form, some propel themselves through the water by their umbrella shaped bells. Some such as the lions mane jellyfish, which we regularly see in Hebridean waters, have long stinging tentacles that are used to disarm their prey. Others, like the moon jelly simply look like pulsating disks floating in the water column. Children are always intrigued to hear that they don’t have bones, heart or brain and that their mouth and anus are one and the same and that they can’t actually see. They are, however, particularly efficient feeders and take advantage of some of the many problems that our ocean ecosystems face. Many jelly species seem able to cope with the rising temperatures that global warming brings and can cope in less oxygenated waters that are caused by agricultural run-off and human waste. Overfishing of small fish such as sandeels and anchovies results in less competition for the zoo plankton which they both feed on. Conversely the removal of the numbers of their predators higher up the trophic scale, such as turtles and tuna has also probably contributed to jellyfish proliferation.
It is the link to these predators that encourages my dreaming here in the Hebrides. I know that two species that I have yet to record here are currently in the region to take advantage of the large amount of food in our waters during summer months, including jellyfish. Both the ocean sunfish and leatherback turtles have been seen in the region in the past few weeks. Leatherback turtles are particularly partial to jellies!
An Ocean SunFish
So if you are travelling on a CalMac ferry over the coming weekend then keep your eyes peeled for turtles, sunfish and those fascinating jellies. And if you are out and about on the beach you could take part in the Marine Conservation Society’s citizen science project The Great British Jellywatch weekend!
ORCA Wildlife Officer - Hebrides