Alert over fish kill at Coalpit Dam

Anglers have been asked to avoid fishing at Coalpit Dam near Naseby, in Otago, as the cause of a fish kill there this week is investigated.

Otago Fish & Game was alerted by concerned anglers to issues at the dam.

Anglers described seeing ‘’sluggish” trout sitting in shallow water close to shore and swimming inverted and on their sides.

Pictured: Dead rainbow trout before they were retrieved from Coalpit Dam, near Naseby, on Tuesday, April 17. Photo: Otago Fish & Game

Fish & Game staff visited the site on Tuesday (April 17) and found about 15 dead rainbow trout and a brook char.

Fish & Game ecologist Jayde Couper said a spot check of the water suggested that despite low temperatures, the oxygen levels in the dam were very low.

Most of the dead trout were retrieved by Fish & Game for analysis.

“The trout appear to have been in very good condition before they died,” Mr Couper said.

“We don’t know the cause yet. What seems unusual is that low oxygen levels are often associated with high water temperatures, and in this case the water was cool, at about 12 degrees Celsius.”

After having months of dry weather in Central Otago, the dam was observed to be about 30cm below full. The water’s edge was out about 2 metres in the shallows, Mr Couper said.

Fish & Game has passed on the information to the Otago Regional Council for further investigation.

“In the meantime, we ask that anglers avoid fishing the dam to protect the remaining stressed fish population,” Mr Couper said.

Coalpit Dam is a popular fishing and picnic spot in the Naseby Forest. It was built to store water for gold recovery during the mining era and is now stocked with rainbow trout by Fish & Game.

ORC manager compliance Tami Sargeant acknowledged it might be distressing for the public to see dead fish but asked that they did not handle or remove the fish.

ORC was notified of 10-15 dead fish through ORC’s Pollution Hotline this morning.

“ORC incident responders have been on site at the Coal Pit dam today. They have taken water samples, and initiated standard responses to these type of events to assess what the cause of the fish deaths might be,” Ms Sargeant said.

“It’s likely that results from the water testing won’t be available until later next week.”