Jelly Blubber: Facts, Habitat & More

Jelly Blubber (Catostylus mosaicus), also known as Blue Blubber or Blue Blubber Jellyfish, is a common scyphozoan jellyfish found along Australia’s eastern coast.

See Jelly Blubbers Up Close at SEA LIFE Sydney

Meet these mesmerising creatures in person! Plan your visit to SEA LIFE Sydney and explore our jellyfish zone, home to the striking Jelly Blubber, Moon Jellyfish, and Upside-Down Jellyfish.

Scientific Name

Catostylus mosaicus

Habitat

Coastal and estuarine waters along eastern and northern Australia, especially around Sydney Harbour and Moreton Bay

Size

Up to 35cm wide

Lifespan

Several months in the wild; up to 1 year in aquariums

Diet

Zooplankton, crustaceans, fish eggs, and larvae

Sting

Mild sting - can cause slight irritation in humans, but is not considered dangerous

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What is a Jelly Blubber?

Despite the name, jelly blubbers aren’t blubbery at all. They're soft-bodied marine animals known for their firm, dome-shaped bells and short, frilly oral arms. Like other jellyfish, they belong to the Phylum Cnidaria and are invertebrates, meaning they have no bones, heart, or brain.

Easy to Identify

Jelly Blubbers have a smooth, dome-shaped bell that can grow up to 35cm wide, making them one of the larger jellies you’ll spot near the shore.

Instead of long, trailing tentacles, they have eight frilly oral arms tucked underneath; these are used for feeding, not stinging.

Their colour depends on where they live. Thanks to symbiotic algae living in their tissues, Jelly Blubbers range from blue in warmer northern waters to brown or cream in cooler southern areas. The algae also help power them by converting sunlight into energy - like a natural solar panel!

💡Did you know? When conditions are just right, jelly blubbers can suddenly appear in the thousands. These massive blooms are common in summer, especially in places like Sydney Harbour.

Ancient Drifters of Australian Waters

Jelly Blubbers are regulars along Australia’s eastern and northern coasts, especially in places like Sydney Harbour, Moreton Bay, and calm estuaries where they gather in large numbers.

But don’t let their gentle drift fool you, these jellies have been around for over 500 million years, making them some of the oldest animals in the ocean. Their ancestors were pulsing through prehistoric seas long before dinosaurs existed.

Large blooms can clog fishing nets. Because of their drifting nature, jelly blubber swarms sometimes disrupt fishing and block boat intakes when they gather in massive numbers.

💡 Did you know?

Jelly blubber polyps can hit “pause” on life. When conditions aren’t right, they shrink into a dormant cyst, surviving for months without growing or feeding. Once the water warms up or food returns, they spring back to life

How They Move and Feed

Jelly Blubbers move with a gentle pulse, contracting and relaxing their bell to push through the water. While they can swim, they often let ocean currents carry them along.

Feeding looks like drifting magic.

Step 1: Capture.

Tiny prey like zooplankton or fish larvae get trapped in mucus and hit by stinging cells (nematocysts) on the oral arms.

Step 2: Transport.

Cilia (tiny hair-like structures) help move the prey along the arms.

Step 3: Digestion.

The prey is funnelled into multiple small mouth openings on the arms, which all lead into the central stomach cavity inside the bell.

Their sting is mild and generally harmless, often compared to a light itch or tingle.

💡During the day, they float near the surface so their internal algae can soak up sunlight and photosynthesise energy.

Anatomy 101

No brain, heart, or lungs

Jelly blubbers might seem simple, but they’ve survived for millions of years using a basic nerve net to sense the world around them. They absorb oxygen straight through their skin, no lungs required.

One opening does it all

Like other jellies, they eat and excrete through a single central opening beneath the bell. Efficient, if a little awkward.

Reproduction and Lifecycle

From hidden polyps to jellyfish blooms, Jelly Blubbers have a remarkable way of multiplying:

Egg + sperm released

Adult jellyfish (medusae) spawn by releasing eggs and sperm into the water.

Fertilised larvae drift

Tiny larvae (planulae) float through the water until they find a surface to settle on.

Polyps take hold

Once attached, the larvae become polyps – small, tube-shaped forms that stay anchored in place.

Cloning baby jellies

When conditions are right, polyps clone themselves and release stacks of baby jellies called ephyrae.

Growing into jelly blubbers

Ephyrae grow quickly into full-sized Jelly Blubbers, ready to feed, drift, and start the cycle again.

💡 Did you know? In jelly blubbers, male jellyfish release sperm into the water, which the female ingests through her mouth. Fertilisation then happens inside her stomach!

What is the lifespan of a Jelly Blubber?

Jelly blubbers usually live for around 2-6 months, drifting through Australia’s coastal waters before completing their short but fascinating lifecycle.

But in aquariums like SEA LIFE Sydney, where conditions are just right, they can live up to 12 months.

Who Eats Jelly Blubbers?

A favourite meal for sea turtles and sunfish
Loggerhead turtles and ocean sunfish love a jelly blubber feast — their thick skin makes them immune to the jelly’s mild sting.

💡 Did you know? Tiny fish and crabs sometimes hide among a jelly blubber’s arms for protection. The jelly’s mild sting keeps predators away while the hitchhikers enjoy a free ride.

Where to see Jelly Blubbers?

Visit the Jellyfish Zone at SEA LIFE Sydney Aquarium to witness the Jelly Blubbers up close!

Plan Your Visit

Want to come face-to-bell with a real-life Jelly Blubber? At SEA LIFE Sydney Aquarium, you can see these stunning drifters up close

You can also see other jellyfish at SEA LIFE Sydney!

Check out their fact pages below

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No, their stings are mild and usually only cause minor skin irritation.

They’re common along the east and north coasts, especially in places like Sydney Harbour, Moreton Bay, and estuaries.

Not the long, stringy kind! Instead, Jelly Blubbers have eight short, frilly oral arms tucked beneath their bell. These arms help them catch and eat tiny plankton and larvae.

Their colour depends on where they live and the symbiotic algae in their tissues. Blue in Sydney, white in Queensland, brown in the north.

Jelly Blubbers don’t bioluminesce like Moon Jellies, but their vibrant colours are beautiful under display lighting.

No - Jelly Blubbers are part of a delicate display and are not in the touch pool.

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