New Zealand screwshell (Maoricolpus roseus)
The New Zealand screw shell has a hard, smooth conical shell up to 9cm in length. It is a native New Zealand species that can survive in a range of different habitats, and has established successful populations in New South Wales, Victoria and Tasmania.
It forms a dense covering on the sea floor with live and dead shells at depths up to 100m, and competes with native shellfish for food.
- Smooth spiralled cone (no beads) up to 9cm long
- Yellow/red-brown in colour, often marbled or streaked
- Twofold Bay and continental shelf off Merimbula and Bermagui
- Vic and Tas
- Lying on, or partially buried in sand, mud or gravel
- Intertidal to subtidal
- From 1-130m depth
- Densely blankets sea floor with live and dead shells
- Can affect growth of scallops and displace native shellfish
Similar native species
These native species may be confused with this marine pest.
Photo: Patty Jansen, Australain Shells
- Broader, rough spiralled shell up to 2-5cm long
- Dull grey colour
- Soft sediments in sheltered waters, estuaries, mangroves, tidal flats, seagrasses
Photo: Holly Barlow, Australian Museum
- Shorter shell, up to 5-6cm long
- More mottled appearance, lighter colouration - white/light brown
- Has fine beads forming ridges around the shell
- Inner continental shelf at depths to 140m
Photo: Patty Jansen, Australian Shells
- Dark brown shell with flaring lip
- Up to 11cm long
- Mudflats and mangrove swamps in esturies
How can you help?
Learn to recognise, and be aware of, the New Zealand screwshell so that you can report any suspected new sighting.
If you see this pest in NSW, please report it immediately
- Note the exact location
- If possible take a photo and/or collect a sample
- Freeze sample in a plastic bag
- Report your sighting