Two species of invasive freshwater clams are in the North Island
Corbicula fluminea was found at Bob’s Landing in the Waikato River near Lake Karāpiro in May 2023 and later in the Waikato River from Lake Maraetai Landing to Tuakau. It was found in Lake Rotomanu, a small man-made lake in Taranaki, in November 2025 as a result of a notification from a member of the public.
Corbicula australis was found in March 2024 in a small man-made lagoon at the Lake Taupō Aqua Park, where it is being eradicated.
Find out more about the freshwater clams (Corbicula)
Technical advisory group report on the invasive clams
Following the first detection of Corbicula, a technical advisory group (TAG) was formed to provide scientific and technical expertise.
The TAG included national and international scientists with extensive experience in freshwater invasion ecology, mollusc control, and experience with Corbicula.
Representatives from Waikato iwi brought important local knowledge and perspectives.
Advice from the TAG provided a foundation for decisions about the management of Corbicula.
The TAG agreed that:
- eradicating Corbicula fluminea from the Waikato River is not feasible with current technologies
- a strategy of containment and suppression is feasible.
It recommended a copper sulphate treatment be used to eliminate Corbicula australis from the lagoon near Taupō. Treatment occurred during March and April 2025. Following this, Biosecurity New Zealand began a two-year plan of treatment and monitoring to ensure eradication of Corbicula australis from the lagoon.
Eliminating this population of clams from the lagoon is feasible because this is an isolated, contained and relatively small body of water. This method is not suitable for eliminating Corbicula from such a large river system as the Waikato River.
Biosecurity response to Corbicula fluminea in the Waikato River [PDF, 824 KB]
Research reports on the freshwater clams
To inform the response and long-term management of Corbicula, Biosecurity New Zealand commissioned NIWA to research the effectiveness of a variety of treatment methods for killing juvenile Corbicula fluminea (less than 2 days old). We also commissioned NIWA to conduct a survey of Corbicula fluminea to collect data on population density, habitats occupied, and depth profiles in which they are found. This will ensure future suppression trials are designed appropriately.
Treatment trials for killing juvenile Corbicula fluminea [PDF, 1.8 MB]
Corbicula fluminea suppression trial: step one baseline [PDF, 5.4 MB]
Independent research on Corbicula fluminea
The Cawthron Institute has published research on habitats in Aotearoa New Zealand that may be suitable locations for Corbicula fluminea to establish.
Although not funded by Biosecurity New Zealand, this research will be useful to both Biosecurity New Zealand and our partners to inform ongoing surveillance of the clam.
Earth Sciences New Zealand research programme
Earth Sciences New Zealand (formerly NIWA) has a $10 million research programme on Corbicula fluminea. The focus of the research is to understand the potential impacts of the clam and develop innovative interventions and control methods.
