Clubbed tunicate
| Common name: | Clubbed tunicate |
| Scientific name: | Styela clava |
| Management programme: | Unwanted organism |
Report this pest!
If you think you have seen this pest, we need to know. Please report it.
Clubbed tunicate (Styela clava) can form dense colonies of up to 1500 individuals per square metre, competing for space and food with native species such as mussels and oysters. They are highly effective filter feeders, preying on the larvae of commercially important fisheries species and impacting native biodiversity. Clubbed tunicate can grow rapidly on marine farming lines, vessel hulls, and other structures, increasing costs for maintenance, harvesting, and fuel.
This pest spreads via vessels either as:
- adults attached to boat hulls (fouling)
- larvae in ballast water or carried by water currents.
It has been detected in Otago, found on artificial structures in Otago Harbour. It has not been detected in Southland, and efforts are focused on preventing its spread further south.
- Size: Up to 16 centimetres long.
- Appearance: Long, club-shaped body on a tough stalk with a leathery, knobbly surface. Colour ranges from brownish-white, yellowish-brown, to reddish-brown. It often appears fuzzy underwater.
- Distinctive features: Two closely spaced tubes (called siphons) at the top of the body, usually surrounded by warty little bumps.
- Habitat: Commonly found from the shallows up to 25 metres deep. Clubbed tunicate attaches to rocky coastlines, reefs, boat hulls, piers, pontoons, and underwater farming structures. Prefers sheltered sites but can be found in semi-exposed waters.
Late summer to early autumn (January to April). This period often coincides with peak settlement and when individuals are most visible. Growth is typically rapid during warmer months, making colonies more prominent.
It is an offence to breed, knowingly communicate, exhibit, multiply, propagate, release, or sell, an unwanted organism (Biosecurity Act 1993).
ORC is currently developing a marine biosecurity programme and needs to obtain more information on species distributions before pursuing management options.
If you think you have spotted clubbed tunicate, please let us know.
Report this pest!
If you think you have seen this pest, we need to know. Please report it.
Preventing the spread of clubbed tunicate is the best strategy, as removal of invasive marine pests is both difficult and expensive.
Cleaning your craft and gear for biosecurity purposes is an important way to help protect the marine environment. Just as regular maintenance keeps your equipment in good condition, biosecurity cleaning keeps the ocean healthy for everyone.
The three main types of marine biosecurity cleaning for boaties are:
Report this pest!
If you have seen or suspect the presence of this pest we need to know. Please report it.
Unwanted organism
An unwanted organism is not managed under the ORC Pest Plan but may be controlled as part of our Biosecurity Strategy.
Protect our Paradise
Do you know what’s lurking beneath your boat? The ORC Biosecurity team works hard to stop harmful pests from spreading in Otago’s coastline and helps people learn how to keep these pests out.
November 2019
PDF | 5 MB
The Otago Regional Pest Management Plan focuses on dealing with harmful pests that impact our environment, economy, and communities. It identifies species like rabbits, wallabies, gorse, and wilding conifers that cause problems on our land. Guided by the Biosecurity Act 1993, the plan works with stakeholders to set rules and controls for managing pests. Through consultation, it aims to protect our region's unique ecosystems and species from the damage caused by these invasive organisms.
October 2025
PDF | 919 KB
Clubbed tunicate (Styela clava) can form dense colonies of up to 1500 individuals per square metre, competing for space and food with native species such as mussels and oysters.
www.orc.govt.nz/clubbedtunicate
