Black scar oyster

• Magallana bilineata is a large rock oyster belonging to the Ostreidae family of salt-water bivalve molluscs. The shell can grow to 18cm in length and are variable in shape but can often be likened to an oval or pear formation.
• The lower attached shell valve is deeper (cup-shaped) than the top shell valve. The top shell valve has a series of flat frills that easily break-off in dead shells.
• Black scar oysters are not able to be easily distinguished from other tropical rock oysters such as native rock oysters until they reach their distinctive size being larger than other species. This makes identification in the early stages of the life cycle difficult and significantly limits options for selective treatment as a control measure.
• The area inside the shell where the adductor muscle attaches is black.

• The black scar oyster grows attached to hard objects in brackish shallow intertidal or subtidal waters at depths of 0 to 300 metres.

• Black scar oyster has been detected in Mission Beach, Mourilyan Harbour, Cairns, Port Douglas, Cooktown and Elim Beach.
• Black scar oysters are found abundantly in the western Pacific Ocean, from the Philippines to Tonga and Fiji, and is an economically important species cultured extensively in the Philippines.

• The life cycle takes 18 to 24 months for the oysters to become adults or grow to market size, approximately 7.5cm, however Magallana bilineata can grow up to 18cm in length.

The black scar oyster fouls submerged and floating infrastructure including pylons, pontoons and boats with the ability to occupy disturbed habitats including shallow subtidal sites in quiet locations. However, little is known about the potential invasiveness and impacts of Magallana bilineata.

Biosecurity Queensland continues to investigate the extent of the incursions, which may inform future control, monitoring or treatment measures.

Environmental

• Competes with native species for space.

Economic

• Fouling of wharf pylons, pontoons, marinas and marine aquaculture farms.

Look. Report. Protect.

Marine biosecurity—everyone plays a part.

• Clean your boat regularly.
• Check for marine pests on structures and surrounds.
• Report any suspected marine pests.

Slipway operators, vessel inspectors and vessel owners should regularly and thoroughly check and clean vessel hulls, looking out for pests or growth. Pay particular attention to the nooks and crannies of your vessel including internal seawater systems.

Inspect, clean and dry equipment and gear before moving to a different location. This includes pots, nets, fishing or diving gear, anchors and ropes.

If you think you have seen black scar oyster, report it immediately to Biosecurity Queensland on 13 25 23. Until an authorised officer contacts you, take reasonable and practical steps to prevent it from spreading.

• Black scar oyster is considered biosecurity matter under the Biosecurity Act 2014.
• By law, everyone has a general biosecurity obligation (GBO) to take all reasonable and practical steps to prevent or minimise the risk of Black scar oysters spreading.