Have you ever seen a jellyfish laying, stranded on the beach? Chances are if you visit the Oregon Coast in the mid-late Summer months, you will see them. Most people look, poke, or just walk right on by. But every once in a while you might wonder if there is anything you could do to help it get back to safety of it's salt water home. In this article we will cover the do's and don'ts of helping a stranded Jellyfish. In this article we will discuss one of Oregon's most common Jellyfish species: the Aurelia Aurita, commonly known as the Moon Jellyfish. This article is for educational and awareness purposes.
First off, lets discuss how the Jellyfish breathe and absorb water:
"Aurelia does not have respiratory parts such as gills, lungs or trachea, it respires by diffusing oxygen from water through the thin membrane covering its body. Within the gastrovascular cavity, low oxygenated water can be expelled and high oxygenated water can come in by ciliated action, thus increasing the diffusion of oxygen through cell." (Rees, W. J. (1966). The Cnidaria and Their Evolution. London: Academic Press. pp. 77–104.)
When a Jellyfish becomes stranded on shore and the water begins to evaporate off of the Jellyfish, the jellyfish begins to lose it's potential oxygen. Though the jellyfish may be out of the water, it is not immediately dead. Rather, its a process of losing oxygen, over a period of time until the jellyfish runs out of Oxygen and dies. More information here: http://www.beachstuff.uk/stranded_jellyfish.html
Some marine biologists agree that "a washed up jellyfish is either dead or dying. Even if you return it to the water, it will "almost certainly die." (Richard Pierce https://www.quora.com/What-do-you-do-when-you-find-a-jellyfish-washed-ashore). Though there is a good chance that it will not survive being placed back into the water, Richard Pierce's statement "Almost certainly die" implies that there is a slight chance that a jellyfish returned to the water, after becoming stranded, can survive.
Why do Jellyfish Become Beached?
Jellyfish can swim but they are by no means strong swimmers. Jellyfish are primarily carried by ocean currents, tides, and winds. These factors are influenced by climate change and determine the course of these jellyfish. Often times, during the summer months, strong winds and currents push these jellyfish to shore where they are left during a receding tide. "Jellyfish tend to travel in groups, called blooms, and sometimes rough winds, swells and currents send them to shore at once."(https://www.islandpacket.com/news/local/news-columns-blogs/untamed-lowcountry/article229891689.html)
Does Returning a Stranded Jellyfish to the Water Harm the Food Chain?
Let's consider the following: In the Yaquina Bay, Oregon, USA, Moon Jellyfish frequently become beached in the summertime. While beached they are regularly surrounded by Bears, Raccoons, Gulls, Crows, Eagles, Vultures, Heron, Crabs, Amphipods, and other marine vertebrate and invertebrates.
A 2019 study, thoroughly documented by photographic and video evidence showed that during a 6 hour period of being out of water, 2 medium sized (3-6 inch) Moon jellyfish were beached during low tide and recovered by the water during high tide, 6 hours later; Through the entirety of being on shore, there was no evidence that any animal or insect attempted to consume or come into contact with either of the 2 jellyfish. Even when there were crabs and amphipods only a few inches away and birds only a few feet away. No shore animals showed any interest in eating these highly visible and pungent smelling jellyfish.
In conclusion to this study, it was determined that, in this particular area, during mid-late summer, given that there are other food options available to shore animals; shore animals do not consume these particular jellyfish as part of their regular diet. Rather, the shore animals in this area feast on the abundance of kelp, crabs, clams, sand shrimp, mud shrimp, amphipods, sea worms, decaying fish, decaying seals, and other decaying sea and land animals.
Though it is HIGHLY Discouraged, for safety reasons, returning a freshly beached jellyfish back to the water does one of two things: Gives the jellyfish a very slight chance to survive or keeps the jellyfish fresh longer so that it can be consumed by animals that eat jellyfish as part of their regular diet. We will discuss what animals eat jellyfish as part of their regular diet in the next paragraph.
What Animals Eat Jellyfish as part of Their Regular Diet?
In short, Jellyfish are most commonly eaten by other jellyfish, fish, sharks, turtles and other ocean dwelling creatures.
Further, Aurelia Aurita are known to be eaten by a wide variety of predators, including the ocean sunfish (Mola mola), the leatherback sea turtle (Dermochelys coriacea), the scyphomedusa Phacellophora camtschatica,[Strand, S. W.; Hamner, W. M. (1988). "Predatory behavior of Phacellophora camtschatica and size-selective predation upon Aurelia aurita (Scyphozoa: Cnidaria) in Saanich Inlet, British Columbia". Marine Biology. 99 (3): 409–414. doi:10.1007/BF02112134][Towanda, T.; Thuesen, E. V. (2006). "Ectosymbiotic behavior of Cancer gracilis and its trophic relationships with its host Phacellophora camtschaticaand the parasitoid Hyperia medusarum" (PDF). Marine Ecology Progress Series. 315: 221–236. doi:10.3354/meps315221] and a very large hydromedusa (Aequorea victoria).[Arai, M. N. (1997). A Functional Biology of Scyphozoa. London: Chapman and Hall. pp. 68–206. ISBN 978-0-412-45110-2.] Recently it was reported from the Red Sea that Aurelia Aurita was seasonally preyed upon by two herbivorous fish.[Bos A.R., Cruz-Rivera E. and Sanad A.M. (2016). "Herbivorous fishes Siganus rivulatus (Siganidae) and Zebrasoma desjardinii (Acanthuridae) feed on Ctenophora and Scyphozoa in the Red Sea". Marine Biodiversity. 47: 243–246. doi:10.1007/s12526-016-0454-9] Moon jellies are also fed upon by sea birds, which may be more interested in the amphipods and other small arthropods that frequent the bells of Aurelia, but in any case, birds do some substantial amount of damage to these jellyfish that often are found just at the surface of bays (Floating in the water).
Find more information here: http://www.whateats.com/what-eats-jellyfish
Why You Should Avoid Touching A Jellyfish
Jellyfish are very fragile animals and may tear easily. Only experienced jellyfish handlers should try moving these animals. Further, Jellyfish can sting, even after death. Everyone reacts to jellyfish stings differently and a sting can be life threatening. If you are stung by a jellyfish, seek medical attention immediately.