Introduced seaweed

Aquarium caulerpa (Caulerpa taxifolia) is an introduced aquatic pest in South Australia and listed as a noxious species.

It is bright green seaweed with stems that grow up to 200 fronds, as long as 3 metres, which look like feathers or ferns.

Fish do not eat the weed because it contains a toxin. This seaweed is a serious threat to:

• native sea-grass meadows
• bottom-dwelling communities
• fish breeding grounds.

Infestations in SA

The weed was found in West Lakes, and the Port River near the Jervois Bridge, in March 2002. It was eradicated from West Lakes.

The infestation continues in the Port River despite many attempts to eradicate it. More outbreaks were found in the Port River Estuary in 2004. A containment area was enforced in 2011.

See the map for exact description and coordinates for the Port River Estuary containment area.

How it spreads

The weed can start a new colony from one square centimetre. Pieces of the weed can survive up to 2 weeks out of water. This means it can easily spread between bays and waterways on boats, or fishing equipment.

Under the Fisheries Management Act 2007, penalties apply for people caught intentionally translocating or possessing the weed in any SA waters.

Avoid spread

Take these steps to avoid spreading the weed:

1. Avoid boating nearby, or disturbing beds of the weed.
2. Inspect any equipment used in the Port River before using it in any other area.
3. Wash ropes and other equipment after use in plastic bins using freshwater and bleach.
4. Inspect diving and boating equipment for the weed before and after use.
5. Collect any fragments of the weed that may have attached to your equipment, place them in a biodegradable plastic bag, and dispose of it in a garbage bin. Do not return any fragments to the sea.
6. Do not use the weed in an aquarium.
7. Do not release any water, plants, or animals from a saltwater aquarium into a drain, creek, or the sea.

Report the weed

Reporting is essential to minimise infestations. Take these steps if you find any of this weed:

1. Accurately record the:
   • location, including GPS coordinates if possible
   • depth of water
   • type of bottom the weed was found in (e.g. rocky or sandy)
   • way it was found.
2. Collect a sample and store it in a plastic bag.
3. Report your sighting to the Fishwatch Hotline below.
4. Do not throw any suspicious weeds back into the water. Dispose of the weed in a biodegradable bag and place it in a garbage bin.