w w w. i n d u s t r y. n s w. g ov. a u / i n fo / s e a s q u i r t
DON’T SPREAD AQUATIC PESTS
Watch out for the invasive sea squirt,
Didemnum vexillum
Didemnum vexillum is a type of sea squirt or ascidian that can grow
rapidly, and has the potential to smother both artificial structures and
natural habitats. This pest is of national concern due to its invasive
characteristics, and known impacts overseas. It has not previously
been detected in NSW or elsewhere in Australia.
Identification
This sea squirt is difficult to identify and may be confused with
native species of sea squirt. Its features include:
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Distinctive mustard or orange/yellow colour.
Spongy texture, can feel leathery but not slimy.
Can look like yellow wax dripping from artificial structures.
Surface has dark leaf-like veins with small pores.
Photos courtesy Aquenal Pty Ltd
If you think you have seen this sea squirt – Report it!
Call the I&I NSW 24-hour aquatic pest hotline 02 4916 3877
or email [email protected]
DON’T SPREAD AQUATIC PESTS – Watch out for the invasive sea squirt, Didemnum vexillum
Help stop the spread
Prevent the spread of this pest
• Keep a look out for sea squirts - report new infestations.
• Inspect your boating, fishing and diving gear for
unusual plants or animals .
• Wash your gear on land away from any water body
before visiting another marine location.
• Don’t disturb suspicious sea squirts and don’t return any
sea quirts or fragments of them to the water.
• Abide by any current movement controls (see website
for up-to-date information).
Distribution and habitat
Didemnum vexillum has been reported in New Zealand,
northern Europe, USA, Canada and Japan.
Industry & Investment NSW (I&I NSW) is currently
investigating a suspected outbreak in Twofold Bay on the
NSW South Coast.
It typically grows on hard surfaces in sub-tidal waters and
seems to have a preference for artificial structures such as
piers, wharfs, pilings, buoys, channel markers and boat hulls
and may also be found on breakwalls and natural reefs.
Impacts
Boating / shipping
• Ensure you inspect your vessel for pests prior to leaving
Twofold Bay.
• Use freshwater to clean your boat, hull, trailer and
any gear on land and away from any water body and
dispose of all material collected in a rubbish bin.
Don’t wash debris down drains.
• Check your moorings, anchor, chain and ropes for any
sea squirt fragments and dispose of any fragments in a
rubbish bin.
• Apply antifouling treatments, if appropriate, on the hull
to reduce fouling and the spread of this pest.
• Flush internal seawater systems regularly with
freshwater or an approved treatment.
• Dispose of sewage and bilge water at an approved
pump-out facility.
• Discharge ballast according to Australian Ballast Water
Management Requirements, which recommends
discharging as far as possible away from any land mass,
and in water at least 200 m deep (see www.aqis.gov.au
for further information).
Divers
The sea squirt has the potential to quickly foul boat hulls
(requiring frequent dry dock cleaning and treatment),
artificial structures (piers, wharfs, breakwalls and moorings)
and has the potential to smother natural reefs and areas of
shellfish aquaculture.
Where did it come from?
It is not known how the suspected sea squirt arrived in NSW.
Outbreaks of this sea squirt have previously been recorded
in New Zealand and the United States, and it is thought
that overseas travel by ships and yachts may have been
responsible for those incursions.
What is being done?
I&I NSW is currently developing a management and
eradication plan for this species, including potential control
and eradication options.
• While diving, watch out for any suspicious growths on
hard surfaces, in particular artificial structures such as
piers, channel markers, mooring lines and boat hulls.
• Don’t disturb suspicious sea squirts as small pieces
can break off and form new colonies.
• Check your gear for any sea squirt fragments and wash
thoroughly in freshwater, ensuring any debris does not
re-enter the waterway.
Fishers
• Check your anchor, chain and ropes for any fragments
of the sea squirt.
• Dispose of any sea squirt fragments in a rubbish bin.
Don’t disturb suspicious sea squirts and don’t return
any sea quirts or fragments of them to the water.
• Before going to a new location, wash down your
trailer, boat and fishing equipment with freshwater
away from any water bodies.
If you think you have seen this sea squirt – Report it!
If you think you’ve seen Didemnum vexillum take a good note of its location
(GPS points if possible), take photos (showing the full colony, plus close ups
showing fine detail) and report it immediately!
Call the I&I NSW 24-hour aquatic pest hotline 02 4916 3877
or email [email protected]
For further information
See www.industry.nsw.gov.au/info/seasquirt
or email [email protected]
9945 March 2010