MPI investigation into Northland pipi deaths inconclusive

Thousands of pipi washed up dead in March this year.

Northland hapū have shared their “grave concerns” after an investigation into thousands of dead pipi at a popular shellfish-gathering spot at Whangārei Heads remains inconclusive.

The event in Pataua is the second one after thousands of pipi washed up dead in 2022.

“I think there needs to be a thorough analysis of what’s happening in the awa,” said kaitiaki Dr Arvay Armstrong-Read after an MPI investigation into the deaths did not find a specific cause.

Representing Te Waiariki, Ngāti Korora, Ngāti Takapari Hapū Iwi Trust, Armstrong-Read expressed “grave” concerns for the wellbeing of the awa which was considered a taonga and bore cultural significance for their tribe.

On March 8, residents near the Pataua awa reported a strong smell coming from the river. They soon discovered thousands of dead and dying pipi 300m north of a bridge.

The locals informed the local hapū and MPI which collected samples of pipi and cockles affected, a week later.

Biosecurity New Zealand team manager aquatic health Dr Mike Taylor said tests ruled out the involvement of any exotic diseases.

However, the mass death event was possibly due to several factors such as changes in water temperature, salinity and oxygen levels.

His team’s investigation confirmed their observation after test results on cockles’ digestive system showed signs of being impacted by possible “environmental factors.”

Taylor noted there was a higher likelihood of observing such mortalities in the summer months as shellfish were known to spawn then.

He explained that spawning was a highly strenuous event and potentially made them vulnerable to the changes in the environment.

As well, changes in seawater temperature or changes to nutrient availability could directly affect shellfish health through thermal stress and food availability, he said.

Dr Mike Taylor says it's important that MPI continue to investigate mortality events so that exotic or emerging diseases can be ruled out. PICTURE/Michael Cunningham

“Indirectly, these types of changes can result in sudden algal blooms which may also impact their health.”

Climate change could result in extreme weather events like storms, heavy rainfall and marine heatwaves.

“All these factors in combination can impact vulnerable shellfish populations,” Taylor said.

Armstrong-Read agreed.

She said a huge number of people visiting the area during summer was also a worry as any slight changes in the environment could affect the molluscs.

“Then we are aware of other factors like runoffs from farms, homes, high sedimentation. It’s a combination of things.

“What’s troublesome is that when these things happen our whānau who rely on the kaimoana as a source of survival are the most affected.”

MPI confirmed that the recent mortality involved factors that cannot be readily prevented from occurring in the future.

The kaitiaki said that based on the recent developments their hapū was in the process of formulating a monitoring plan that they intend to carry out later this year.

“The idea is to use localised knowledge of our whanau living there to keep a check on the quality of pipi from time to time.

“And for our mahi to work effectively we do need to be resourced, something we don’t have in abundance.”

Taylor noted that the recent mass death event was similar to the pipi mortality in 2022, where multiple “environmental stressors” or factors were held responsible.

“These factors cannot be readily prevented from occurring. However, we can work on our preparedness to respond to such events quickly.”

He said they were closely working with the trust.

MPI has offered training workshops to better understand such events. And how to collect viable samples and work together to develop a process for reporting such events in the future, Taylor said.

Avneesh Vincent is the crime and emergency services reporter at the Northern Advocate. He was previously at the Gisborne Herald as the arts and environment reporter and is passionate about covering stories that can make a difference. He joined NZME in July 2023.