This freshwater mollusc (also known as Asian gold clam) was discovered along a stretch of the Waikato River in May 2023. Biosecurity New Zealand is working with iwi and other partners to decide future actions.

Keep reading to find out more about the clam and how you can help to prevent it from infesting Otago’s waterways.

These freshwater molluscs (also known as freshwater gold clam) reproduce rapidly and form large populations that can clog water-based infrastructure such as electric generation plants, irrigation systems, and water treatment plants. Corbicula has been implicated with billions of dollars of economic damage overseas. They are filter feeders that have the potential to affect biodiversity and compete with native species for food. 

Otago’s waterways are modelled to be suitable for clam establishment.

The two species of Corbicula, C.australis and C.fluminea are native to Australia and Eastern Asia respectively, with the latterwidely established in North and South America and Europe.Overseas, this clam has proved difficult to control and eradication has never been achieved.

Freshwater gold clams were first found in the Bob’s Landing area of the Waikato River near Lake Karāpiro in early May 2023, and identified as Corbicula fluminea. Since then, Corbicula fluminea has been confirmed in the Waikato River from Lake Maraetai Landing to Tuakau. Corbicula australis has been found in a small, contained water park near Taupō.  Biosecurity New Zealand is working with iwi and other partners to decide future actions.

Keep reading to find out more about the clam and how you can help to prevent it from infesting Otago’s waterways.

Why not? Freshwater gold clam are small filter-feeding shellfish that eat deposits from the river or lake bed and accumulate toxins in their gut. Because of this, they are not safe for human consumption.

• Freshwater gold clams are quite distinctive and easily identified, as there are no similar looking New Zealand freshwater clam species.
• The adult clams are 2cm to 3cm in length and are typically dirty white, yellow, or tan.
• They have an obvious ribbed texture on the shell.
• They are found in freshwater or brackish water. They are able to tolerate a wide range of temperatures and salinities.
• Freshwater gold clams can be found within the water, sitting on top of sandy or muddy surfaces, or buried shallowly within them.
• Freshwater gold clams can be found within the water, sitting on top of sandy or muddy surfaces, or buried shallowly within them. You may see their shells partly exposed, or their syphons (their breathing tubes) sticking out from the sediment. 
• They can also be found amongst debris, such as leaves, that may have settled on the riverbed. 
• The adult clams are 2cm to 3cm in length and are typically dirty white, yellow, or tan. They have an obvious ribbed texture on the shell.

You must notify the Otago Regional Council or the Ministry for Primary Industries if you suspect the presence of this organism

If you think you've seen the freshwater gold clam:

• Note the location.
• Take a photo (if possible).
• Contact:
  • • Ministry for Primary Industries on 0800 80 99 66 or,
    • Complete the online reporting form at Ministry for Primary Industries  

If you are using the online reporting form, you'll need to start by saying you are a member of the public, that you want to make a report about 'a marine or freshwater issue' and then select 'freshwater fish or crustacean' from the dropdown box that will appear.

Then you will be taken through some further questions including contact information and asked to load your images.

If you fish, swim, boat or row, follow the Check, Clean, Dry guidelines to help stop the spread of this clam to other rivers and lakes through New Zealand. Before moving to another location at the river, or to another river or lake:

Check

• Remove anything visible including clams, weed, or mud. Drain all water.

Clean

• Wash down your gear and craft with tap-water onto grass beside the river or lake, or at home – not into a stormwater drain system. This will flush off clams that can be too small to be seen.
• For gear made of absorbent materials (for example clothing, wetsuit), which will stay wet longer, you should do a hot wash (above 45 degrees) or pop it in a freezer until solid.

Dry

• Allow gear to dry to touch, inside and out, and then leave it to dry for at least 5 days before going back in a river or lake.
• Dry areas inside the watercraft where water has pooled, for example with an old towel, and then leave the craft to dry for at least five days. The hull of a watercraft will dry when towed.

Note: The 'Check, Clean, Dry' advice may be adjusted as further technical information becomes available. Refer to the manufacturer’s instructions for gear and any commercial treatments.