The Manganui o te Ao River is incredibly picturesque and has extremely clean water flowing off bush-clad Mt Ruapehu. Along with the Retaruke and other smaller mountain rivers it holds high numbers of whio. The Retaruke and Manganui o te Ao River catchments are one of eight security sites identified in the National Whio Recovery Plan (2007) as a priority for whio management.
This project is funded by the Central North Island Blue Duck Conservation Charitable Trust. It was set up as part of a mitigation package between Genesis Energy, DOC and Forest & Bird during the resource consent renewal process for the Tongariro Power Development.
Where we have come from
In 2002 a trial was run on the Manganui o te Ao River to formulate the criteria for an intensive five year project. This began with investigating the impacts of predator control on the whio population and testing a three trap line model aligned parallel to the river.
Apart from losing chicks to natural threats and predators such as floods, harriers, falcons, and eels, predation by stoats is almost undoubtedly the number one threat to whio. Other threats include rats, hedgehogs and ferrets.
With the cooperation of local landowners and farmers for the first year of the project, one single river trap line was set up, servicing over 10 km of river. Monitoring and banding of adult and fledging juveniles was carried out to understand how the population changes over time and the effect that predator trapping was having. By the third year landowners had granted permission for the other two lines to be deployed.
When the trial finished in 2008, the focus shifted to more intensive trapping and less monitoring.
Additional extensions upstream and downstream to the traplines have been carried out following confirmation of improved whio survival in areas protected by stoat traps. Approximately 35 km of river area is now protected enabling around 38 pairs of whio, depending on the season, a greater opportunity to produce and raise young in a relatively predator-free environment.
The 2009/10 season on the Manganui o te Ao River started well with a warmish winter which encouraged some early breeding and nesting. A dramatic weather change in October took us all by surprise and seriously affected the newly hatched broods. Due to this, most pairs came out of October with reduced brood numbers.
Planning for trap-lines extensions are underway with around 550 trap operating at present. An upsurge of ferrets is causing particular concern in one section and some larger traps (DOC 250’s) are being introduced.
Due to one of the locally trained whio workers successfully securing permanent employment with DOC, an opportunity to train another local arose. DOC has recently taken on Raetihi local Kane Low who has been a real find, taking to the demanding role of trapping, and monitoring whio in all weathers with enthusiasm. Under the guidance of another local, Rufus Bristol, he has been a quick learner and a sponge for Rufus’ considerable knowledge and experience.
What we do
Traps are serviced two times per month from September to February (the blue duck breeding season) and once in the other months. DOC staff and contractors also spend less time monitoring the whio population now they are confident trapping is providing the necessary protection.
We are now at a point, where micro-chipping and banding of the birds as a permanent way of marking them is no longer necessary, reducing the stress of netting and handling the population.
Staff have an ongoing advocacy role with farmers, landowners and the local school, keeping them informed of the season’s breeding results, whio management, and numbers of stoats and other predators caught.
Public usage and recreational fishing in the area is high and staff also keep visitors aware of the threat of didymo to whio habitat and methods for cleaning gear between catchments.
Whio "open days" at Rautiti Domain through the summer, hosted by DOC staff from Whanganui and Tongariro, have proved very popular with locals and visitors alike.
You can help
Manganui o te Ao River is a popular destination for many recreational groups, including mountain bikers, rafters, campers and fishers. You can help by making sure to "check, clean and dry" your gear to prevent didymo from reaching these pristine waterways, as well as leaving dogs at home. Fishers need to be very careful with lines and hooks, which must be removed from the waterway and surrounding area.
You can also help by reporting any concerns to: