[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 .
Lizards have also been detected and the area is habitat for long-tail bats (pekapeka) all of which are at risk from possums, mustelids and feral cats.
While whio have not been detected for some time, a young male duck was reported in the nearby Waingawa catchment in 2020.
The stream is also listed in Greater Wellington's Regional Freshwater Plan as a waterway with important trout habitat.
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.