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A gold rush it may be, but not the type that’s welcome anywhere near a steel mill.
Biosecurity New Zealand has confirmed the presence of the invasive freshwater gold clam in the Ruakohua stream tributary near the Glenbrook Steel Mill.
The news reinforces the importance of preventing the movement of freshwater pests between waterways and Auckland Council’s surveillance programme says Samantha Hill, council’s GM Environmental Services.
“While this detection is connected to the existing Waikato River incursion, it’s still disappointing to see invasive freshwater gold clam in the Auckland region.”
The detection is thought to be linked to the existing Waikato River incursion as the mill is (effectively) connected to the lower Waikato through consented water takes – permission is granted to take water from one region to use in another.
Exactly how the incursion occurred may seem simple, but hard work will now be needed to check its spread.
“Once freshwater pests become established, they are extremely difficult to remove, which is why preventing their spread remains our best defence,” Hill adds Auckland Council, mana whenua and New Zealand Steel are now working together to determine the extent of the clam’s presence at the site and assess the risk of any further spread, with support from Biosecurity New Zealand and Waikato Regional Council.
The invasive freshwater clam (Corbicula) was discovered in the Waikato River in 2023.
It threatens native ecosystems while also clogging such infrastructure as hydro power generation, water treatment plants and irrigation systems.
The clams spread quickly – each one is able to have up to 70,000 juveniles each year.
Their microscopic young can easily attach to, and travel on, wetsuits, kayaks and other equipment used in the water unless it is thoroughly dried and treated.
To help prevent the spread,‘check, clean, dry’ all watercraft and gear when moving between waterways, council advises.
It is also important to be familiar with Controlled Area Notices (CANs) in place for the Waikato River.
Additional information about these pests and how to avoid spreading them is available by searching ‘clams’ at Conservation Auckland’s website, tiakitamakimakaurau.nz.
