Why a discovery in the Mangawharariki River is being hailed a conservation success

Dwarf galaxiids have been found in the Mangawharariki River.

The discovery of a thriving population of little-known fish in the Mangawharariki River in Rangitīkei has been hailed as a success for conservation initiatives.

Rangitīkei Rivers Catchment Collective (RRCC) has found the dwarf galaxiids during a stream health assessment.

Catchment co-ordinator Louise Totman said the fish were a good indicator of healthy water and a lack of predators.

The Mangawharariki flows from the Ruahine Range and meets the Rangitīkei River at Mangaweka.

RRCC is a farmer-led incorporation designed for farmers to work collectively to improve waterways and soils and enhance biodiversity.

The Mangawharariki runs through the farms of RRCC’s Mangawharariki sub-catchment group, which has fenced off the main part of the river and monitored water quality since January 2020.

“It was extremely rewarding finding the fish,” Mangawharariki sub-catchment group chairperson Greg Clifton said.

The Department of Conservation said dwarf galaxiids were small non-migratory fish native to New Zealand.

Their name comes from the galaxy-like gold flecks and patterns on their backs. Unlike whitebait, some non-migratory galaxiid species live out their entire life in the stream or river in which they hatched.

“Galaxiids are a perfect snack for introduced trout but, because of the old hydro power dam at the bottom of the Mangawharariki River, trout can’t get up this far,” Totman said.

Horizons freshwater and partnerships manager Logan Brown said finding the galaxiids was a sign of good water quality.

“Generally the places we find them are gravel-bottomed streams with very little sediment, which is sort of what the Mangawharariki River has, so it is definitely one of the indications we look at for healthy water.”

Since 2018, RRCC has built a significant regional dataset of water-quality monitoring.

“Three to five years of data has been collected from nine of our 22 sub-catchment groups and this will continue to grow year on year,” Totman said.

RRCC farmer members undertake monthly water-quality monitoring at 88 sites across its 700,000-hectare catchment.