Hundreds of fish have mysteriously died in the river flowing through the Mt Somers village.

The fish started appearing the weekend before New Year’s, said village resident Duncan Humm.

“It looked like a complete kill of everything.”

A Fish & Game representative and Environment Canterbury have confirmed both invasive trout and native galaxiids turned up dead in the river, connected to the Ashburton District Council stock water race.

The number of dead fish sits above 350, and reminds Humm of a similar phenomenon from 2021.

“There was a spraying contractor who dumped wastewater into the river, and killed all the fish.”

In 2021, a truck driver for Harrison Spraying Services released an agrichemical into the stock water race, poisoning hundreds of fish and landing the business a $120,000 fine.

Last time, the council had issued warnings to keep animals away from the water, so Humm was surprised no similar warnings had come through yet.

“The dead fish were found from our place and past the new water treatment plants.

“But we haven’t heard any directive from councils not to feed [from] it yet.”

Environment Canterbury had been contacted about the fish last Saturday, and began investigating the day after, he said.

“ECan aren’t my favourite people in the world, but I was really stoked to see them move so swiftly.”

Acting ECan compliance manager Lauren Hamilton said there was “no present risk” to residents.

“(As part of the investigation), our staff will continue to monitor the area and advise if there is any change to the situation.”

She confirmed that among the dead trout, native Canterbury galaxias and upland bully had been found.

ECan could not comment further as the investigation is ongoing

"However, from an observational perspective, we can now confirm there are fish swimming in the area".

By Anisha Satya