Mystery over thousands of eels found dead in stream

Thousands of eels were found dead in a freshwater stream in New Zealand.

It is the second mass eel death in the country this year, sparking an investigation by environment officials under the Ministry for Primary Industries.

More than 3,500 juvenile eels were discovered dead in the Kauritutahi stream, on the northernmost flank of North Island.

While the first incident was attributed directly to a toxic pollutant, what killed the eels in Kauritutahi was not immediately clear.

Authorities suspect it may be due to a ‘stress event’ linked to climate change, but this remains unconfirmed, the New Zealand Herald reported.

Rissa Williams, Biosecurity NZ acting team manager, said: ‘It is possible that the mortality could have been caused by a stress event.’

Meanwhile, Hona Edwards, a member of a local guardian group that monitors the stream, took it upon himself to test the water.

Algae buildup was also observed in some stream sections with limited water flow, indicating it was warming up.

We noticed some algae build up which generally is due to the stream water warming up,” according to Hona Edwards, a member of a local guardian group that monitors the stream.

Mr Edwards said: ‘Then the biggest percentage of the stream was observed to range from very limited to no water flow.

‘When there is no flow, the dissolved oxygen reduces, and the toxins build up in the waterway.’

This comes after more than 2,600 eels were found dead in the Low Burn Stream and smaller nearby streams just off the Mataura River in February.

It sparked an Environment Southland investigation into the cause of the mass casualty of the taonga, which uncovered a poison in the waterway.

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