Two proposed new power schemes on the Nevis River could threaten a species of galaxid which has been discovered in the area.
Pioneer Generation has plans to build two hydro dams on the river. They would produce up to 45MW.
The first hydro lake upstream of the Nevis Cutting would fluctuate in height by 5m and Fish and Game Otago policy adviser John Hollows said for fish that would be like living in a toilet bowl.
The lower dam would act like a head pond, pushing water through to the power house.
Restrictions on hydro electric development include a provision to allow fish to migrate from the lower Nevis into the upper section of the river.
A population of galaxids was found in the Nevis River and its tributaries in the mid-1990s and further investigations have shown it is part of the Gollum galaxias species.
Cr Dan Rae presented a report carried out by Golder Associates to a Fish and Game council meeting in Clyde this week.
The report confirmed that the population of Gollum galaxias in the Nevis was the only one of its kind in Otago waters, due to a geographical accident, in the past, as all others were in Southland.
The species had been recently classified from nonthreatened to in gradual decline. If a hydro dam was built it would split the population and prevent interaction.
The current Water Conservation Order (WCO) that protects part of the Nevis River does afford the population some protection.
However the report said the construction of a hydroelectric power scheme in the Nevis Valley represented an uncertain level of detrimental impact on the Gollum galaxias population.
There is no provision in the WCO to specifically protect the population of Gollum galaxias present within the catchment, as the information was not known to the WCO commissioners when the Conservation order was imposed.
The Minister for the Environment has accepted an application from Fish and Game for an amendment to the WCO which would protect the river from dams. That application will be heard soon, Mr Hollows said.
