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.