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Black-striped mussel (Mytilopsis sallei)

This exotic marine pest is listed on the Australian Priority Marine Pest List because it can form dense populations and foul marine infrastructure. It is not known to have established populations in Australia; a population found in Darwin in 1999 was eradicated, although the species has since been detected on vessels and in seawater systems.

Key facts

Type: Pest animal, invertebrate.

Native to: West Indies and the Caribbean coast of Central and South America, from Yucatan to Venezuela, including part of southern Florida.

Established in: NT.

Other names: Black-striped false mussel, Black striped false mussel, Mytilopsis sallei.

Identification

  • A small mussel, usually reaching around 25 mm long, with an elongated shell.
  • Shell colour varies from white, cream or bluish-grey to brown or black; small specimens may have brown zigzag markings.
  • The shell is thin and easily crushed, and the two valves are slightly unequal, with the left valve fitting inside the right.
  • Individuals attach to hard surfaces with byssal threads and may occur in dense clusters.

Where it lives

It favours sheltered tropical and subtropical coastal waters, especially shallow intertidal and subtidal habitats and hard surfaces such as wharves, pontoons, vessel hulls and seawater systems.

Why it matters

  • Dense growth can foul vessel hulls, ropes, nets, moorings, wharves, pontoons, pipes, seawater intakes and cooling systems.
  • It can form dense stands that smother or exclude other species and reduce biodiversity.
  • Fouling of marine infrastructure can cause serious problems for maritime and aquaculture industries.
  • It can become the dominant fouling organism in shallow coastal habitats.

How it spreads

  • Vessel biofouling is a major introduction pathway, including growth on hulls, niche areas and internal seawater systems.
  • Larvae can disperse with currents or be carried in ballast water and water retained in vessel spaces and systems.
  • Fouled structures and equipment, including anchors, moorings, ropes, floats and nets, can carry mussels to new locations.

Control methods

  • Report suspected detections promptly to the relevant state or territory marine biosecurity agency and follow its directions; early detection and action are important.
  • For small, accessible infestations, trained crews may remove mussels by hand or scraping, collecting all material for secure disposal on land.
  • Remove fouled movable structures for approved treatment on land where practicable; contain wash-down waste and prevent mussels or larvae returning to the water.
  • Use agency-led surveys to define the infestation, restrict movement of potentially contaminated vessels and equipment, and monitor treated sites for new mussels.

Site hygiene and welfare

  • Before moving a vessel or equipment from an affected area, inspect and clean submerged surfaces and seawater niches, and treat internal seawater systems as directed by biosecurity authorities.
  • Keep potentially contaminated water, fouled gear and removed mussels contained; do not transfer them to another waterway.
  • Use methods set out in the national model codes of practice and standard operating procedures for the species.
  • Coordinate control with neighbours and the local government biosecurity plan, as isolated effort is quickly undone by reinvasion.

Classification by state

  • Australia (national): Priority marine pest. On the Australian Priority Marine Pest List, agreed by all governments as a marine pest of national concern. National priority exotic pest. On the National Priority List of Exotic Environmental Pests, Weeds and Diseases, so any new detection should be reported straight away.
  • Queensland: Prohibited matter. Report it to Biosecurity Queensland on 13 25 23 within 24 hours and do not move or deal with it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Prohibited matter. It is an offence to deal with it, and you must notify NSW DPIRD as soon as you become aware of it.
  • Victoria: Noxious aquatic species. Declared a noxious aquatic species under the Fisheries Act 1995, so it must not be brought into Victoria, kept, sold, moved or released into waters. Report any sighting to the Victorian Fisheries Authority on 13 FISH (13 3474).
  • South Australia: Noxious species. Declared a noxious species under the Fisheries Management Act 2007, so it must not be brought into South Australia, kept, sold or released, and it must not be returned to the water alive. Report any sighting to PIRSA FISHWATCH on 1800 065 522.
  • Western Australia: Noxious fish. Prescribed as a noxious fish under the Fish Resources Management Regulations 1995, so it must not be brought into WA, kept, sold or released. Report any sighting to FishWatch on 1800 815 507.
  • Tasmania: Declared pest. It is a declared pest under the Biosecurity Act 2019 (Tas). Report sightings to Biosecurity Tasmania and follow any management requirements.
  • Northern Territory: Not a declared pest. Not on an NT declared or prohibited list. Check with the NT Government before keeping, moving or releasing it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources