Inanga, the most common whitebait species, lay their eggs (spawn) in the base of long dense grasses along stream banks where the saltwater meets the freshwater during a spring tide, which typically occurs once a month from March till July. The eggs remain above the water level until the next spring tide when they hatch and are washed out to sea.
Inanga use the same spawning sites in streams each year, so by identifying and protecting these places, we can increase the number of eggs, juveniles and eventually adult fish.
Of the five native fish species that make up whitebait, inanga, giant kokopu, kōaro and the shortjaw kokopu are either in decline or threatened. However, work is underway in Tairāwhiti to restore the habitat these fish require to lay their eggs in.
The Inanga Spawning Habitat Restoration Project began in 2015 and has been well supported by the Tairāwhiti Environment Centre, Enviroschools, Whitebait Connections, Wai Restoration, and the local community.
The Pakowhai stream in Muriwai has been recognised as one of the best spawning sites in the Waipaoa catchment area and is a key stream for the project. The spawning zone along the Pakowhai is only a few hundred metres long, whereas the spawning zone along the Te Arai River is almost 1.8km in length.
In collaboration with the landowners and project leads (Jamie and Katie Foxley), the spawning area along the Pakowhai was fenced off from stock to allow the grass to grow long. Native sedges (grasses) such as Carex Geminata/Rautahi were planted along the spring tide mark to provide more natural habitat for the fish to spawn. Shrubs and lower growing trees such as Harakeke, Toetoe, Koromiko, Kanuka and Ti kōuka were planted on the upper bank to increase biodiversity along the stream bank. It is important to ensure the shrubs and smaller trees are planted far enough back from the spring tide mark to ensure that they do not shade out the long grasses which are essential for spawning.
This year, Gisborne District Council in partnership with Rongowhakaata Iwi Trust have been monitoring the spawning success along the Pakowhai Stream. In August, Rongowhakaata Iwi Trust planted 700 native sedges, shrubs and trees along the stream banks to help restore habitat for native fish. There are plans to establish pest control along the stream to prevent rats and other predators from eating the inanga eggs as they sit in the long grass waiting for the next spring tide.
“We’ve engaged in this mahi to restore vitality back to our Tūranga spaces; cultural, relational and environmental,” says Rongowhakaata Iwi Trust environmental specialist Soraya Pohatu.
“Our goal is to restore the mana of the land and protect the mauri of the stream.”
Council Environmental Scientist and Inanga Habitat Restoration Project Manager Olive Steven said that fencing off waterways, allowing the grass to grow long and dense is the first step to improving spawning success. Planting native sedges and small shrubs can help to improve the spawning success by re-introducing the native habitat back to these special spawning sites.
If you would like any further information on spawning locations around Tairāwhiti or would like to get involved in inanga spawning habitat restoration please get in contact with GDC project coordinator Olive Steven Olive.Steven@gdc.govt.nz