Mangātarere Stream is a small gravel-bed stream in central Wairarapa, New Zealand, that originates in the Tararua Ranges. It is located close to the township of Carterton and is the main tributary to the Waiohine River. The Waiohine flows into the Ruamāhanga River, southeast of Greytown.[1] [2]
The Ruamāhanga catchment is home to 79 native bird species, 29 in the nationally threatened and 50 in the non-threatened categories and includes breeding grounds for black-billed gull (tarapuka), banded dotterel (pohowera) and black fronted dotterel . The regenerating and established native and bush remnants in the Upper Mangātrere harbour a range of these native species or habitat important to them. Lizards have also been detected and the area is habitat for long-tail bats all of which are at risk from possums, mustelids and feral cats. Long-tail bats have the highest threat ranking of Nationally Critical. The Upper Mangatārere Stream is also the last known long-term site for whio in the region. While whio have not been detected for some time, a young male duck was reported in the nearby Waingawa catchment in 2020.[3]
Eleven species of native freshwater fish and one native decapod (koura) have been recorded within the Mangātarere Stream catchment. Of the 11 fish species, four (longfin, eel, dwarf galaxias, lamprey and brown mudfish) are classified as threatened species by the Department of Conservation. Koura are also classed as a threatened species.
The stream is also listed in Greater Wellington's Regional Freshwater Plan as a waterway with important trout habitat. It is considered by Fish and Game to be a valuable brown trout spawning and rearing stream in the Wellington region, and is recognised as important in maintaining the trout fishery of the entire Ruamāhanga Catchment.
A Mangātarere Stream Catchment Water Quality Investigation was conducted by Greater Wellington Regional Council between 2008 and 2010 in response to concerns about poor water quality. The results of surface water quality sampling over September 2008 to August 2009, indicate a decline in water quality with distance down the Mangātarere Stream towards the Carterton Township. Nutrient concentrations exceed the Australian and New Zealand Guidelines for aquatic ecosystems (commonly known as the ANZECC guidelines).
The investigation identified that the stream's status as an important trout fishery, and habitat for four species of threatened native fish, is being adversely affected by storm water and waste water discharge from Carterton township and from nutrient leaching and stock access by dairy and drystock farmers. Riparian planting of native vegetation along the stream is being encouraged to assist filtration of nutrients and provide shade for native aquatic biodiversity.