Experts baffled as thousands of eels found dead in New Zealand

Authorities in New Zealand are investigating an unfortunate incident in which thousands of juvenile eels — an elongated ray-finned fish — washed up in the Kauritutahi stream, reported the New Zealand Herald.

The massive deaths marked the second time in the current year.

Officials under the Ministry for Primary Industries expressed their concerns and commenced a probe to find the cause of death of over 3,500 juvenile eels.

The incident on the northernmost flank of North Island was attributed to the toxic pollutant, however, experts are not ruling out the effects of climate change that may cause stress events.

Biosecurity NZ acting team manager Rissa Williams said in the report: "It’s possible the mortality could have been caused by a stress event," adding that "this could be connected to a trap and transfer programme, but all possibilities were on the table."

Josie Boyd, Northpower Network’s chief operating officer, said work was underway to understand the cause and any environmental factors at play.

The COO said: "The trap and transfer strategies were continuously reviewed and adapted, but they could only do so much as an eel’s expected survival rate through its migration cycle was very low at 4 to 8%."

A local guardian group member Edward told the outlet that the stream's water quality had declined in the past couple of years, linking it to climate change.

He said: "We noticed some algae build up which generally is due to the stream water warming up."

Cawthron Institute freshwater ecologist Dr Simon Stewart believed that multiple factors such as habitat food and so on were the stress points.

Edwards said: "It’s a signal for all of us to do what we can to improve the health of our waterways in NZ to avoid situations like these."