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What’s with all these Jelly Blubbers

May 30, 2018

Since taking over Shoalhaven River Cruise, I have been very fascinated (and a little creeped out) by the huge numbers of pulsing little Jellyfish that constantly float by the Shoalhaven Explorer. I’ve been asked ‘what’s with all these Jelly Blubbers’ by so many passengers.  I’ve heard many different stories about times that our passengers have come into contact with them and it blows my mind that people would even consider swimming in the water with them but I grew up around a freshwater river so no Jellyfish there!.  So I finally did some research and this is what I found out.

What are they actually called?

They have a few different names including Jelly Blubbers, which I thought was just a nickname that people used for all jellyfish, and blue blubber jellyfish but their scientific name is Catostylus mosaicus.  They have a dome-shaped bell that can grow up to 35 cm in diameter and usually have 8 club like arms, each of which contains several mouths which transport food to the jelly blubbers stomach. They range in colour from very light blue/white to dark purple and burgundy and this colouring is derived from pigments produced by the Jellyfish itself.

Where can you find them?

This species is native to eastern Australia, distributed along the Eastern Coast from Queensland to Victoria.



These Jelly Blubbers are often found in dense swarms, swimming just below the surface of the water as we can see in the Shoalhaven River. They have limited control over movement but can use a contraction-pulsations movement of the bell-like body to help propel them with the tidal flow. Some species actively swim a lot of the time, while others are more passive. Jellyfish are composed of more than 90% water and most of their umbrella mass is a gelatinous material – the jelly – called mesoglea.

Do Jelly Blubbers consume food?

The Jelly Blubbers eat mainly plankton, small fish, some crustaceans, and small particles in the ocean water. They feed continuously and grow to adult size fairly rapidly. After reaching adult size they spawn daily if there is enough food in the ecosystem. In most jellyfish species, spawning is controlled by light, so the entire population spawns at about the same time of day, often at either dusk or dawn.

They do not need a respiratory system as their skin is thin enough to oxygenate their body by diffusion, which is really pretty cool.

I wasn’t able to find any information about the lifespan of this particular type of Jellyfish but the consensus is that Jellyfish usually live from a few hours to a few months. I’ve also been told that the Jellyfish in the Shoalhaven River will be in abundance for a period of time and then a large rain event will wash them all out to sea. Once this occurs they may not be seen back in the River again for a number of years.

My Conclusion!

All I know for sure is that they are creepy little critters that have been known to ‘sting’ leaving an itchy welt that can last for up to a week. And this means that this ‘fresh water river girl’ will not be swimming in the Shoalhaven River while they are pulsating their way back and forth.

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