Local iwi are fearing the worst for the mauri of their ancestral waters after invasive freshwater gold clams were detected in a Waiuku awa, sparking urgent biosecurity and cultural concerns.
Roimata Minhinnick, lead negotiator for mana whenua Ngāti Te Ata Waiohua, says the biggest concern for the iwi is the harm the species could bring and whether solutions can be found to protect the life force of the water.
“Ko te āwangawanga ko ngā mōrearea o te iwi nei. He aha ngā āhuatanga o tērā pipi, te mōrearea ki runga i te mauri o te wai,” he says.
How the incursion unfolded
The invasive freshwater gold clams were detected at New Zealand Steel’s Glenbrook mill in South Auckland, prompting authorities to investigate two pipelines that carry Waikato River water to the site.
Biosecurity New Zealand confirmed it is the first sign of the species in the Auckland region, brought to the Ruakohua stream by one of two pipes connected to the elbow of the Waikato River for on-site work. While the water is treated upon arrival, confirmation on how the species survived and how far it has spread is still pending.
Auckland Council states they are working closely with mana whenua and New Zealand Steel, with support from Biosecurity New Zealand and the Waikato Regional Council, to determine the full extent of the issue.
The growing threat
First detected in Lake Karāpiro and the Waikato River in 2023, and having since spread to locations like Lake Rotomanu in Taranaki, gold clams present a severe multi-faceted threat:
- Ecological damage: They deplete water sources of nutrients, reduce calcium levels (which can cause arsenic to become more prevalent), accumulate heavy metals, and outcompete native species for space and food.
- Rapid reproduction: They can self-fertilise and produce over 70,000 juveniles per year, making their microscopic spawn easily transportable via clothing, animals, and equipment.
- Infrastructure risk: They clog filters and pumps, causing significant economic issues, and are notoriously difficult to eradicate, with no solid solutions yet found.
While Biosecurity New Zealand spokesperson Dr Catherine Duthie notes the clams wouldn’t survive long in salt water if they reached the Manukau Harbour, and believes the incursion is contained within a non-recreational stream running through farmland and commercial land, concerns from the community remain high.
“It’s not a place that’s used recreationally. The likelihood of it then moving out elsewhere is exceedingly low, and we think we caught that quite early; we’ll be able to do something about that,” she says.
Minhinnick warns that the threat goes far beyond environmental damage, striking at the core of the iwi’s identity and history.
“He kōrero anō ki roto i ngā āhuatanga o te wai, ko te mauri tētehi, ka whakaaro anō e mātou ka mate tērā wai, ka mate te mauri, ka ngaro ngā kōrero, ngā hītori, ngā pāngatanga o mātou ki te whenua rā, ki te wai rānei tērā ki a mātou.”
Minhinnick emphasises that all parties must work collaboratively to protect the area.
The group is now waiting on results from eDNA tests to determine the spread and is examining whether a second pipeline connected to Maioro, carrying both water and iron sand to the mill, shows any signs of the clams.
Mana whenua are also questioning whether the species could breach brackish waters in the Manukau Harbour that mix with freshwater and are not entirely protected from on-site water.
NZ Steel say that they have followed all advice and guidance available from MPI in mitigating the spread and presence of clams on site.
“New Zealand Steel shares concern about the spread of this new organism. This recent detection is disappointing, and we are committed to working with the Council and mana whenua to determine the extent of the clam’s presence at the site and assess any risk of further spread with support from Biosecurity New Zealand and Waikato Regional Council.”
