Aquatic pests: marine and freshwater

In July 2025, black scar oysters (Magallana bilineata) were found living in the Cullen Bay Marina in Darwin, NT.

Black scar oysters are not native to Australia. They have been established in Queensland since 2020.

They likely came to the NT on domestic boats.

Impact

In Queensland, no specific impacts to marina operations, infrastructure, oyster farming or the environment have been reported.

NT Fisheries is monitoring the oysters for:

• population growth
• spread
• any impacts.

What it looks like

Inside the oyster, there is a black mark where the flesh joins the shell.

From the outside, they can be hard to tell apart from other native oysters.

Size

They can grow over 210mm long and can be larger than native rock oysters, which grow over 140mm.

To learn more about identifying them, get the marine pest field guide PDF (2.6 MB).

Report it

If you think you have seen black scar oysters, follow these steps.

Step 1. Take photos of the oysters.

Step 2. Note the location where you saw them.

Step 3. Send the photos and location information to the Aquatic Biosecurity team:

• email aquaticbioecurity.@nt.gov.au
• text 0413 381 094
• call 1800 891 136 (24/7).

More information

Black scar oysters are found throughout south-east Asia and the western Pacific Ocean, where they are farmed for food.

They are related to the widely farmed cooler-water Pacific oyster.

For more information, go to the Australian Government's National Marine Pest Information System (NIMPIS) website.