Autopsies ruled out in fish mystery

The Otago Regional Council will not conduct autopsies on fish that died in a Queenstown creek, despite the cause of death remaining a mystery.

On May 1, council pollution officers visited Horne Creek after receiving a report from the public and found up to 150 brown trout and one native galaxiid dead in the waterway.

A council investigation, which included appealing to the public for information, hoped to determine the cause of the mass kill but has shed no light so far.

Water samples were taken from Horne Creek in the days following the deaths.

Council compliance manager Tami Sargeant said that as the water samples were inconclusive, "no autopsies will be undertaken on the fish", despite some having been kept frozen in Queenstown for testing.

The results might not have revealed a result because the pollutant was no longer in the stream when water samples were taken, Mrs Sargeant said.

The council contacted laboratories and environmental bodies to potentially conduct an autopsy on the fish, but as water samples did not reveal possible pollutants, they "don’t know what to sample for", she said.

"Autopsies on fish after this type of event are hard to undertake as the autopsy itself is unlikely to show anything."

Otago Fish & Game officer Bruce Quirey said it was understandable that autopsies would not be conducted, but it was disappointing a cause had not been determined and nobody could be held accountable.

"If there were traces, such as paint, oil or cement, in the water, then you could test fish samples for those contaminants - otherwise it’s difficult to know where to start," he said.

"The fact is we don’t treat our waterways well enough, and it’s regrettable the perpetrator may have gotten away with it."

lucy.wormald@odt.co.nz