Black scar oyster

• Magallana bilineata is a large rock oyster belonging to the Ostreidae family of saltwater bivalve molluscs. The shells 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 cannot 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 Townsville, 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. They are economically important and cultured extensively in the Philippines.

• It 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. It can 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.

• 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.
• Report any suspected marine pests.

• The black scar oyster is a category 2, 3, 4 and 5 restricted marine pest under the Biosecurity Act 2014. You must not:
  • move it
  • keep it
  • give it away
  • sell it
  • release it into the environment.

  If you do any of these, penalties may apply.

• You must take all reasonable and practical measures that are under your control to minimise the biosecurity risks associated with dealing with black scar oysters. This is part of your general biosecurity obligation.
• You must report any sightings within 24 hours using 1 of these methods:
  • Report online.
  • Phone Biosecurity Queensland on 13 25 23.