Mystery pollutant kills a dozen eels in a suburban stream on Auckland's North Shore

Monday, 13 February 2017

Ecologist Brett Stansfield

Pollution is to blame for a dozen dead eels washed up on the banks of a suburban stream on Auckland's North Shore, but the pollutant remains a mystery.

A number of Birkenhead residents took to the LeRoy's Bush community Facebook page to express disgust about the January 30 incident.

People posted that it looked as if oil or fat could be the cause of the eels' death.

Water bubbles beneath a dirty film of oil and silt in a polluted urban stream.

Many concerned residents, including Kaipatiki Local Board member John Gillon, reported the incident to the council's pollution hotline, but they were too late.

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Freelance ecologist Brett Stansfield tests three different sites in Le Roys Bush.

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A dozen dead eels were found on the banks of a Birkenhead stream.

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'Auckland Council responded to numerous pollution reports and tested the pH and ammonia levels at the site on January 30 and 31. Both of these came back as normal,' manager compliance resource consents Steve Pearce, adding the pollution had already washed away.

The turbidity of this stream water reads at 60.5, by comparison, drinking water is ideally less than 1.

'This incident highlights the need for immediate reportage of pollution occurrences,' Pearce said.

An autopsy on the eels would not take place because the source of the pollution could not be found, he added.

Freelance ecologist Brett Stansfield tested three different sites in Le Roys Bush stream on February 10. His tests show pollution increased greatly further down the stream.

'If I was a fish, I'd be getting the hell out of here,' Stansfield said at one of the sites.

The 'hardy' nature of eels makes this recent incident even more concerning for Stansfield.

'I have seen eels at the outfall of a wastewater plant - happy as Larry,' he said.

'It must have been a pretty nasty contaminant to kill them.'

Stansfield said earlier and more immediate reporting of stream pollution will lead to more policing; however, preventing pollution at the source is key.

'Water is the receiving environment for everything we do,' he said.

'Everything that is on the road, washes through the stormwater pipes and into the stream.'

Pollution control can be as simple as washing cars on the grass and being wary of what you spill on the ground, he said.

For pollution concerns, contact Auckland Council's 24-hour pollution hotline 09 377 3107.