Claire Concannon meets the latest addition to the Zealandia ecosanctuary family - toitoi, or common bully. Zealandia CEO Dr Danielle Shanahan explains why these little fish will be an important part of the freshwater ecosystem, and what their ambitious 100 year plans are to restore the mouri or lifeforce of the entire Kaiwharawhara catchment.

The native birds are loud and proud at Te Māra-a-Tāne, Zealandia.

They flit amongst the canopy, call from the branches, preen on their perches, and even stroll across the paths.

But today we look past the manu, and instead focus on the humble freshwater fauna living their quiet lives amongst their boisterous feathered brethren.

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Most of Zealandia's freshwater areas are in fact manmade. The Karori upper and lower dams, completed in 1908 and 1878, were in use as drinking water reservoirs until the 1990s, when they were decommissioned due to earthquake risk.

Now part of the fenced ecosanctuary, the team at Zealandia have taken on the task of restoring some of the native wildlife that once would have been present in this catchment.

The Kaiwharawhara stream is born at the top of the sanctuary, collects in the dammed upper reservoir, feeds down through a man-made wetland area to the lower reservoir and then winds its way through the western suburbs and down the Ngaio Gorge, finishing its journey at Wellington Harbour beside the ferry terminal. So, an incredibly modified, urban landscape.

To restore this valley to a hint of its former glory will take a lot of work. But CEO of Zealandia, Dr Danielle Shanahan, remains undaunted: "This is a 100-year vision of restoring the mouri or lifeforce of this absolutely incredible catchment." This collaborative project - Kia mouriora te Kaiwharawhara, Sanctuary to sea - will involve dealing with historic landfills within the catchment, providing fish passage for native ika to be able to move upstream, and advocating to ensure future developments are freshwater friendly.

For Danielle, it must start at home. She and the Zealandia team have been working hard to restore the upper reservoir (now called Roto Māhanga), the lower reservoir (referred to as Roto Kawau after the shags that hang out there), and the wetland area in between.

The most recent addition is toitoi, the common bully, to Roto Māhanga. These are cute speckled brown fish that are an important part of another freshwater resident's lifecycle. Kākahi, or freshwater mussels, sneeze out their larvae which then attach to the gills of fish like toitoi in order to disperse. …

Go to this episode on rnz.co.nz for more details