Mangātarere Stream


Mangātarere Stream is a small gravel-bed stream in central Wairarapa, New Zealand, flowing from the Tararua Ranges to the Waiohine River near Carterton, which joins the Ruamāhanga River southeast of Greytown. The stream provides habitat for native birds, fish, freshwater crayfish, and long-tailed bats, supports a brown trout fishery, and faces ecological pressures from agricultural runoff and township wastewater, with riparian planting used to mitigate impacts.

Ecology

Terrestrial fauna

The Ruamāhanga catchment supports 79 native bird species, including 29 classified as nationally threatened and 50 as non-threatened. The area includes breeding habitat for black-billed gull, banded dotterel and black fronted dotterel. Regenerating and established native forest and bush remnants in the upper Mangātarere catchment provide habitat for a range of these species. Native lizards have also been recorded, and the area supports long-tail bats, which are classified as Nationally Critical and are vulnerable to predation by possums, mustelids, and feral cats. The upper Mangatārere Stream is the last known long-term site for whio in the region, although whio have not been detected in recent years, a young male was reported in the nearby Waingawa catchment in 2020.

Aquatic fauna

Eleven species of native freshwater fish and one native decapod species, kōura, have been recorded within the stream's catchment. Four of the fish species are classified as threatened by the Department of Conservation. Kōura are also listed as a threatened species.

Fisheries

Mangātarere stream is listed in Greater Wellington's Regional Freshwater Plan as a waterway with important trout habitat. Fish and Game New Zealand identifies the stream as a valuable brown trout spawning and rearing stream in the Wellington region and considers it significant for maintaining the trout fishery of the wider Ruamāhanga catchment.

Water quality and management

Between 2008 and 2010, Greater Wellington Regional Council conducted a Mangātarere Stream Catchment Water Quality Investigation in response to concerns about declining water quality. Surface water sampling undertaken from September 2008 to August 2009 show a decline in water quality downstream toward the Carterton Township, with nutrient concentrations exceeding the Australian and New Zealand Guidelines for aquatic ecosystems.
The investigation found that the stormwater and wastewater discharge from Carterton, along with nutrient leaching and livestock access associated with dairy and drystock farming, were adversely affecting the stream’s ecological values, including its role as trout habitat and as habitat for threatened native fish species. Riparian planting of native vegetation has been encouraged to reduce nutrient runoff and provide shading to support for aquatic biodiversity.