The tribunal is conducting a month-long hearing which will decide the fate of the Nevis River and whether dams should be permitted on the river in the future.
The New Zealand and Otago Fish and Game Councils have applied to amend the Water Conservation Order on the river, so damming or diversion of the river flow would be prohibited.
The existing order paves the way for hydro-electricity development to be considered and energy company Pioneer Generation has plans for two dams on the river.
If the tribunal decides to amend the water conservation order, dams will be banned.
Giving evidence before the tribunal yesterday Royal Forest and Bird Protection Society Otago Southland field officer Sue Maturin said the river and its surroundings supported ecosystems containing several nationally threatened species.
"These are among some of the most threatened ecosystems in New Zealand and the world,"Ms Maturin said.
"These now rare ecosystems have scientific importance and are a national priority to protect."
Dams on the Nevis would flood the habitats of two nationally endangered birds - black-fronted tern and black-billed gull - and also the threatened banded dotterel.
As well, it would affect endangered plants such as Myosaurus minimus (New Zealand mousetail), Leptinella (button daisy) and Carex uncifolia (tufted sedge).
The Nevis Valley was also a stronghold for what was believed to be a new species of skink.
"Only a few dozen of these rare animals have ever been found and it is uncertain how widespread they are," Ms Maturin said.
They lived in the area which would be flooded if a dam was created, obliterating their habitat and vegetation.
It was possible the Nevis skink would be identified as a new species, in which case the valley was nationally important for the protection of the species, she said.
The society's Central Otago-Lakes branch executive member, Anne Steven, also highlighted the importance of the valley and the river.
"In our view, the river cannot be developed for hydro power and have its values protected and sustained at the same time, because its values are dependent on the river retaining its natural characteristics . . ."
Ms Steven said.
The group was concerned there had been no full and systematic assessment of the natural and cultural features along the river.
There was still much to be discovered, she said.
• Day 9
Tribunal: Richard Fowler (chairman), Carolyn Burns and Rauru Kirikiri.
Application: To amend the existing Water Conservation Order to prevent damming or diversion of the Nevis River.
Players: NZ and Otago Fish and Game Councils want the changes, Pioneer Generation and TrustPower are among those in opposition.
Yesterday: Evidence heard from Otago Goldfields Heritage Trust vice-president Mike Floate, Royal Forest and Bird Protection Society Otago Southland field officer Sue Maturin, the society's Central Otago-Lakes branch executive member Anne Steven, Central Otago Recreational Users Forum secretary Jan Kelly, Wakatipu Anglers Club president Chris Dore, Glen Callanan and Kate White.
Next week: Evidence from Pioneer Generation witnesses.
Quote of the day: "The waters of the Nevis are some of the most pristine within our local area, and the trout of the most stunning colouration and immaculate condition" - Wakatipu Anglers Club president Chris Dore.
