High temperatures caused fish deaths in South Taranaki waterways, report finds

A report to the Taranaki Regional Council stated more than 80 fish had died in two South Taranaki waterways.

Record high water temperatures and low river levels likely contributed to the deaths of more than 80 fish in two South Taranaki waterways this year, the Taranaki Regional Council says.

A report to the council’s operations and regulatory committee said 27 fish died in the Waingongoro River and a further 55 fish were found dead 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 investigation revealed that water temperatures in both rivers were the highest on record and were elevated for several days around the time the dead fish were discovered. Temperatures were up to 5C warmer than usual for the time of year.

River levels were also low for 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.

Taranaki Regional Council 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. 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. 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 the number reported, given that some could have been scavenged or washed out to sea before the investigation.