Fact Sheet
Brown Jellyfish
(Phyllorhiza punctata)
During summer and early autumn,
as Perth temperatures rise and the
marine influence over the estuary
increases, Brown Jellyfish increase
in numbers and may form a dense
layer near the water’s surface. This
jellyfish does not inflict a painful
sting on humans, but it is best not
to touch it.
Description
Brown Jellyfish are characterised by a bell that is usually saucer-shaped and brown with white
spots. These jellyfish are brown in colour due to a dinoflagellate alga that lives in the jellyfish
tissues1. The jellyfish’s mouth is under the bell and surrounded by long stinging tentacles. These
animals have a stomach cavity and reproductive organs inside the thick jelly of the bell. These
jellyfish grow to a width of 50cm.
Distribution
Brown Jellyfish are widespread in oceans and estuaries in the IndoPacific, in the tropical western
Atlantic and in the eastern Pacific2. They occur in Australian water from north Queensland
through the south-east to the south-west. They occur in the Swan Canning Riverpark, but not
other estuaries along the west coast. Although they are able to move by making pulsing
movements, ocean currents and ship movements have a big influence on their distribution. They
are thought to have been introduced into the Swan Canning Riverpark by ships that serviced the
Swan River colony between 1829 and 18372. However, the southward movement of jellyfish with
the Leeuwin Current is also a plausible explanation for their presence here.
Habitat
Brown Jellyfish usually occur near the surface of oceans and estuaries where their food is most
abundant. They are most common in the Swan Canning Riverpark in summer and in areas
where salinity exceeds 25ppt. They are absent when surface waters are dominated by low
salinity water after winter rainfall2.
Fact Sheet
Biology
Brown Jellyfish feed on small planktonic algae and zooplankton (including eggs and larval fish) 1.
Adult jellyfish (medusa) produce eggs and sperm that are released into the water. After
fertilisation eggs develop into larvae called planula that attach to rocks. These grow into polyps
that eventually release medusa when they are approximately 1mm in diameter. This usually
occurs between November and December and the medusa are large enough to reproduce
sexually within 6 weeks. The polyps of this species have not been located but are thought to
occur in the Swan Canning Riverpark1.
Two fish species are known to be associated with these jellyfish. The larvae of the Mosaic
Leatherjacket and Trevally make use of the jellyfish for shelter, transportation and planktonic
food, which is trapped and killed in the jellyfish’s stinging tissue3. The young fish are immune to
the stinging tentacles and can even eat them. This association does not appear to benefit the
jellyfish, nor does it seem to do them any great harm. When they are a few centimetres long
these fish leave their hosts and occupy habitat elsewhere.
Threats
Often caught in prawning nets and left on shorelines. Often played with by children. Although
jellyfish cannot feel pain, they can become stressed if they are touched too much.
Conservation
This is thought to be an introduced species to the Swan Canning Riverpark
References:
1. Brearley, A. (2005). Ernest Hodgkin’s Swanland: Estuaries and Coastal Lagoons of South-western Australia.
UWA Press, Perth.
2. Rippingale, R.J. and Kelly, S.J. (1995). Reproduction and survival of Phyllorhiza punctata (Cnidaria
Rhizostomeae) in a seasonally fluctuating salinity regime in Western Australia. Marine and Freshwater
Research: 46, 1145-51.
3.
Storrie, A and Thomson-Dans, C (2000). Discovering the Swan River and the Swan Estuary Park.
Department of Conservation and Land Management, Perth.