A second fish kill in Otago in only a week has highlighted the vulnerability of urban waterways, Otago Fish & Game says.

A member of the public alerted Otago Fish & Game to dead trout seen in Bullock Creek behind Wānaka residential sections on Thursday afternoon (April 18).

Fish & Game officer Mason Court said staff inspected and found six dead trout within a 50-metre stretch of the creek downstream of Roche St.

The fish appeared to have been dead for one or two days, and there were no visible causes of death, he said.

“While we don’t know exactly what’s happened, it was likely the fish were killed by toxins entering the stream,” Mason said. “This looks like a localised water quality issue.”

A longfin eel and juvenile brown trout were found alive in the same stretch of water later that evening, suggesting that whatever had killed the other fish had been rapidly diluted by the fast-flowing creek, he said.

The spring-fed creek in the heart of Wānaka was an important spawning habitat for brown and rainbow trout, and supported native fish.

Before this latest incident, the naturally pristine creek has been flooded with sediment runoff since the expansion of urban development above the wetland, Mason said.

“Bullock Creek originates in Fish & Game’s QEII-covenanted Wānaka Hatchery Springs wetland, where thousands of hours of community volunteer work has gone into restoring habitat,” Mason said. 

“But it takes a whole village to look after our waterways.”

He said the incident was “a timely lesson of how careful we all need to be to keep contaminants, such as cleaning fluids, paint or chemicals, out of waterways”.

The Wānaka fish kill follows the discovery of 15 dead trout at Coalpit Dam, near Naseby, last Monday (April 15).

The Bullock Creek fish were provided to the ORC to be tested, and the results are still pending.

Fish & Game thanked the member of the public who called about the dead fish.

PHOTO: Otago Fish & Game