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Dead man's fingers (Codium fragile)

Introduced Codium fragile is widely spread along the Victorian coast and has also been recorded in Tasmania and South Australia. It can form dense stands and foul shellfish and aquaculture equipment, with potential effects on native biodiversity, habitats and fisheries.

Key facts

Type: Weed, aquatic.

Native to: Japan is the type locality..

Established in: QLD, NSW, ACT, VIC, TAS, SA, WA.

Other names: Codium fragile ssp. tomentosoides, Codium fragile ssp. capense, Codium mucronatum var. tomentosoides, AcanthoCodium fragile.

Best time to act: In Port Phillip Bay, reported densities are highest from January to May and lowest from July to December; the report does not specify a general treatment season.

Identification

  • It is a large, branching green alga, usually 15 to 60 cm tall but sometimes reaching almost 1 m.
  • Its branches divide into pairs and are about 3 to 10 mm in diameter.
  • A spongy basal holdfast attaches the alga to surfaces such as rocks, shells and artificial structures.
  • Juvenile plants appear as moss-like mats, and adult plants can grow from fragments.
  • Look-alike: Native Codium subspecies and other Codium species in southern Australian waters can look similar; reliable identification requires microscopic examination of the thalli.

Where it grows

In Australia it occurs in intertidal and subtidal habitats, including protected to semi-exposed areas, and can attach to natural surfaces, shellfish and artificial structures.

Why it matters

  • Dense stands can change local ecology and may reduce native biodiversity.
  • The alga can smother mussels and scallops, potentially preventing their valves from opening.
  • It can foul nets, ropes, aquaculture facilities and other structures, increasing harvesting costs and reducing productivity.
  • Fouling of beaches, pylons and jetties can reduce social amenity.

How it spreads

  • Fragments can reattach and grow into adult plants, and adult thalli can produce vegetative juveniles.
  • Potential transport pathways include shellfish movements, fouled boat hulls, nets and ropes, as well as natural dispersal.
  • The report identifies trans-Tasman shipping as a likely pathway for the alga's incursion into Australian waters.

Control options

  • The report describes chemical treatment as unsuitable because herbicides require prolonged contact, large doses and may cause general ecological damage.
  • Mechanical removal can be non-selective, and fragmentation may help the alga spread.
  • Hand removal is labour-intensive and has been largely ineffective; in Australia it also risks removing similar native Codium species.
  • Prioritise prevention by cleaning shellfish, aquaculture equipment, ropes, nets and boat hulls before they are moved.

Hygiene and washdown

  • Clean boat hulls, ropes, nets and aquaculture equipment thoroughly before moving them, and use wash-down areas where available.
  • Check shellfish and other fishery stock for attached alga before translocation.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • 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: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • 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. This applies in any area of the State except in the Port of Albany. Report any sighting to FishWatch on 1800 815 507.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • 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.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources