More than 40 dead eels and an unexplained whitish growth have surfaced in a South Wairarapa stream, ringing alarm bells for Greater Wellington Regional Council staff and farmers.
GWRC senior communications adviser Rick Marshall said an initial site visit to Whangaehu Stream near Pirinoa ruled out any illegal pollution sources, and that further samples were collected with results expected at the end of the week.
"Several farmers reported the dead eels," Mr Marshall said.
"One land owner identified that it has worsened over the last couple of weeks and they have counted around 40 dead eels some of which are large which is why we are taking this issue seriously."
The site at the stream has low water flows which is known to stress aquatic life, but Mr Marshall said the site was also affected by low oxygen levels in the water, "due to excessive honey dew falling from the willows overhanging the stream because of a massive infestation of invasive giant aphids".
Although there has been some rain in parts of Wairarapa, GWRC monitoring shows it has been extremely dry in South Wairarapa, causing low water flow in some streams.
The total accumulated rainfall, October 2015 to March 2016, has been about 50 per cent of normal and on a par with the lowest recorded over summer in at least the last 30 years, according to GWRC.
High evapotranspiration rates as a result of warm temperatures over summer have added to the water stress.
Rona Te Maari, who belongs to the area's iwi, said over the last three years there had been a lot of dried up riverbeds around Pirinoa. "There are a lot of reasons for this including the drought, but one of the contributing factors, which isn't mentioned very often around here, would be the increase of intensive farming and farmers' need to irrigate their farms."