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The Department of Conservation (DOC) is urging people moving between lakes and rivers to use the Check, Clean, Dry method to help prevent the spread of invasive freshwater gold clams.
The clams, known as Corbicula fluminea, were first found in the Waikato River in May 2023 and have since spread rapidly through parts of the Waikato catchment, including Lake Taupō.
The species reproduces quickly, producing up to 70,000 juveniles a year. It lives in freshwater but can also survive in the salty water found in estuaries. DOC says the clams can attach to absorbent materials, making them easy to spread on fishing, boating and swimming gear.
In some areas of the Waikato River, populations now number in the thousands per square metre, DOC says. The clams disrupt native species, water quality and river sediments, and can also clog up infrastructure such as drinking water supplies and treatment plants, power stations and irrigation systems.
The species was declared an Unwanted Organism under the Biosecurity Act in August 2023. This means it cannot be knowingly spread. Biosecurity New Zealand is co-ordinating a long-term management plan with DOC, regional councils and mana whenua.
Because the larvae are extremely small, measuring about 0.2mm, they are difficult to detect and easy to transport between waterways.
DOC is asking fishers and whitebaiters to limit fishing to one river or to use separate gear when moving between rivers. Fishers are also advised to freeze neoprene gear such as waders to kill any larvae that may remain in residual water.
Check, Clean, Dry
To reduce the spread of invasive freshwater pests, boaties, fishers, swimmers and trampers should check, clean and dry all gear before moving to another waterway. If gear cannot be treated, it should only be used in one location.
Anyone who thinks they have seen invasive clams is asked to note the location, take a photo if possible, and report it to Biosecurity NZ on 0800 80 99 66 or via the MPI online reporting form.
