Exotic freshwater clams can survive in a wide range of environments
Two species of exotic freshwater clams are present in the Waikato region.
- Corbicula fluminea (commonly known as 'gold clams' or 'freshwater gold clams') is native to eastern Asia and is widely established in North and South America and Europe.
- Corbicula australis is native to Australia, where it is common and widely distributed.
Both are found in freshwater. They are found in highest abundance around the edges of lakes and rivers. They can survive a wide range of temperatures and can live in:
- lakes, and rivers down to where saltwater and freshwater mix
- on top of, or buried in, a variety of substrates (for example, gravel, sand, or mud)
- high-oxygen waters.
They are fast breeders and can clog facilities like water treatment plants
These 2 types of Corbicula are prolific breeders, able to produce 400 juveniles a day and up to 70,000 juveniles a year, allowing them to reach extremely high densities in optimal conditions.
This means they can clog water-based infrastructure, such as electricity generation plants, irrigation systems, and water treatment plants. They can also compete with native species for food and space.
Overseas, Corbicula fluminea has proved difficult to control and eradication has never been achieved.
Top: Corbicula australis clam shells (A to E). The picture on the right (A, B, C) shows various sizes of the clam shells to scale. A 5 mm line is shown bottom right for reference.
Bottom: Corbicula fluminea clam shells (F to J). The picture on the right (D and E) shows 2 sizes of the clam shells to scale. A 5 mm line is shown bottom right for reference.
Photo credits: Jean-Claude Stahl and Kerry Walton, Te Papa.
Where the clams have been found in New Zealand
Corbicula fluminea: It was found in the Bob’s Landing area of the Waikato River near Lake Karāpiro in May 2023. It was later found in the Waikato River from Lake Maraetai Landing to Tuakau.
Corbicula australis: It was found in March 2024 at the Lake Taupō Aqua Park in a small man-made lagoon.
