A rainbow trout (file). Photo: 123RF
Record high water temperatures and low river levels are being blamed for the deaths of more than 80 fish in two South Taranaki waterways.
The Taranaki Regional Council says 27 fish died in the Waingongoro River and 55 fish in the Kaūpokonui River in January.
An investigation was launched after members of the public alerted Taranaki Fish and Game to the deaths.
The affected species included tuna (long-fin eel) and trout.
The council investigation revealed water temperatures in both rivers were the highest on record, and were elevated for several days at the time the dead fish were discovered.
Temperatures were up to 5C warmer than usual for the time of year.
River levels were also particularly low for the months of December and January, while oxygen levels in the water were extremely high, reaching levels toxic to fish.
The investigation found no evidence of a pollution incident.
Director for environmental quality Abby Matthews said it was difficult to identify any single cause of the fish deaths.
"It's likely that the combination of high temperatures, low flows and oxygen toxicity all contributed to these events. Unfortunately these types of environmental extremes are likely to become more common with the effects of climate change."
Matthews said the total number of fish deaths was likely to be higher than reported, given some could have been scavenged or washed out to sea prior to the investigation.
"We'd like to thank the public who brought this to our attention so we could respond quickly. It's important we investigate issues such as this and try to find the cause."
Matthews said the council was currently seeking views on freshwater targets for the region's rivers and streams. To have your say, head to [www.trc.govt.nz/helpshapetherules www.trc.govt.nz/helpshapetherules] to see information on targets for E. coli, nutrients and sediment and targets and limits for water take and take part in surveys.
To report pollution or incidents involving Taranaki waterways, please call the council on 0800 736 222 or email [mailto:info@trc.govt.nz info@trc.govt.nz].