Fish disease, pollutants, lead to call for inquiry into Kaipara river health

Dargaville Ratepayers and Residents Association chair Rose Dixon, pictured with vice-chairs Sam Erickson and Jo Floyd, says there needs to be an inquiry into the poor health of the Northern Wairoa River, shown behind them.

Dargaville residents are calling for a government inquiry into high levels of pollutants in the Northern Wairoa River, which could be contributing to an illness in snapper.

Fish with missing flesh, and milky and bloodshot eyes - so ill they have been called “zombie fish” - have been fished out of the Northern Wairoa and other parts of Kaipara Harbour.

While the Ministry for Primary Industries is still investigating what has caused the snapper disease, Cawthron Institute aquatic animal health team leader Dr Kate Hutson said generally, poor water quality can compromise fish immunity.

The Northland Regional Council said water quality in the northern Wairoa is “very poor”.

Data from 2020 to 2023 showed the river failed eight out of 12 standards, including turbidity, total nitrogen, total phosphorus, faecal coliforms, total zinc and total copper.

Dargaville Ratepayers and Residents Association chairwoman Rose Dixon said the poor health of the river, coupled with the “zombie fish”, is massively concerning.

The association is calling for a commission of inquiry, or central government inquiry, to investigate why such high levels of pollution are occurring and what is affecting the fish.

The inquiry needs to look at possible sources of pollution, including wastewater treatment plants along the river, Dixon said.

The Northern Wairoa is said to be the longest navigable river in the country, and, for locals, it is an important source of kaimoana, including flounder, mullet, snapper and shellfish, she said.

“We needed to know what we’re catching is safe to eat; we need to know we’re not going to get severely ill when we go swimming.”

Dixon said pollution and sedimentation in the river have been reported for many years but do not seem to have improved, and the zombie snapper could be a sign of things getting worse.

But the council, which is responsible for monitoring the Northern Wairoa and about half of Kaipara Harbour, does not see any need for a central government inquiry.

A council spokesperson said the issues with the Kaipara Harbour, and all the rivers that drain to the harbour, are well recognised as being related to sediment and the previous Government committed $100 million to start the long-term Kaipara Moana Remediation programme.

Poor water quality in the Northern Wairoa River could be attributed to surface run-off from developed pasture, lack of upstream native bush and erosion, the council said.

However, the catchment includes a number of dairy farm effluent discharges and the Dargaville wastewater treatment plant which is a “potentially significant source of nutrients”, the spokesperson said.

Compliance of both the Dargaville and Te Kopuru wastewater treatment plants have varied over the last 12 months, with both plants fully compliant only about half the time.

“Neither treatment plant has recorded a significant non-compliance, although both plants have recorded minor to moderate consent non-compliances.”

Sediment is master contaminant in Kaipara, remediation leader says

Scientific studies show sediment is the major pollutant in the Kaipara Harbour, said Justine Daw, Kaipara Moana Remediation pou tātaki/chief executive.

“Sediment is a ‘master contaminant’: when soils erode from the land and flow into waterways, the resulting sediment carries with it many other contaminants that can harm ecological and human health, such as phosphates, nitrates and heavy metals,” she said.

Kaipara Moana Remediation pou tātaki Justine Daw says sediment is a ‘master contaminant', carry with it many other pollutants when it enters the water.

An estimated 700,000 tonnes of sediment flow into the harbour each year on average – seven times the natural rate – due to decades of deforestation and land-use intensification, Daw said.

“Sediment smothers riverbeds and the seabed and reduces light penetration into the water, significantly affecting ecosystem health and valued species including shellfish, snapper and seagrass.”

Kaipara Moana Remediation was announced in July 2020 with $100m in central Government funding, to be matched with funds from the Northland Regional Council, Auckland Council and in-kind contributions from landowners.

Two-and-a-half years into delivery, the project has completed or contracted 730km of fencing - more than the distance from Cape Rēinga to Taupō - and planted 1.7 million plants.

The 10-year project has also trained more than 50 people to work with landowners to develop sediment reduction plans and will ramp-up work as it goes on.

Daw said as sediment is a long-term contaminant, it will take years, if not decades, to be able to demonstrate meaningful trends in water quality.

But a similar project in the much smaller Whāingaroa Harbour, near Raglan, planted 2.1 million trees and found sediment in the harbour dropped by 90 per cent and fish catch rates were 50 times better, she said.

Fencing no good without compliance, environmentalist says

Millan Ruka has been passionate about cleaning up waterways for more than a decade and he hasn't seen any improvement. Photo / John Stone

Clean-water campaigner Millan Ruka also supports a government inquiry into the health of the Northern Wairoa, which he said has not been improving for decades.

Ruka started Environment River Patrol Aotearoa in 2010 due to the poor water quality of Kōkopu’s Wairua River, a tributary of the Northern Wairoa.

Since then, he has waded and paddled up rivers to gather evidence of compliance, or non-compliance, and said the smell of effluent from some dairy farms stinks.

While freshwater rules are still being set, the system is already flawed when it comes to compliance of the current rules, both in the Kaipara Harbour and nationwide, Ruka said.

One example of this is the fact dairy farms are checked for compliance just once a year, he said. More than a third of Northland dairy farms were found to be not fully compliant with their dairy effluent consents in 2023.

Ruka said while the fencing and planting with Kaipara Moana Remediation is good, there also needs to be enforcement to ensure stock stay on the right side of the fences, as he has seen plenty of farmers grazing the river side.

The regional council said it has a robust dairy farm effluent monitoring programme, with all Northland dairy farms being inspected each dairy season, to check compliance with either the discharge resource consent or the “permitted activity rule” they are operating under.

“The council undertakes follow-up action on all farms that are recorded as having moderate or significant non-compliances, which may include formal enforcement action,” the council spokesperson said.

The council said if people see dairy cows walking in parts of the Northern Wairoa, or its tributaries, they should report this to council through its Environmental Hotline, 0800 504 639.

Denise Piper is a news reporter for the Northern Advocate, focusing on health and business. She has more than 20 years in journalism and is passionate about covering stories that make a difference.