The galaxiid fish was reclassified in June and was now in the third-highest category of the Department of Conservation's (Doc) threat classification system.
Doc technical support officer Murray Neilson gave evidence during the hearing into whether hydro-electric dams should be allowed on the Nevis River.
A special tribunal has been hearing an application to amend the existing water conservation order on the river. The New Zealand and Otago Fish and Game Councils have sought the amendment, which would ban damming and diversion of the river.
The application attracted 248 submissions and the hearing began in May. So far the hearing has spanned 15 days and it resumed yesterday in Dunedin.
Mr Neilson said the threatened status of flora and fauna was being reviewed and the classification system had been revised.
Smeagol galaxias were now ranked as "nationally vulnerable". Species were classified based on the total number, ongoing or predicted population trends, and the number of mature individuals.
The chairman of the freshwater fish committee that conducted the threat ranking process for Doc, Richard Allibone, said the Nevis population of the fish was stable but restricted to a limited area.
Its ranking was upgraded because of its limited distribution, which made it vulnerable to habitat loss, climate change and predators.
Potential hydro development had not been taken into consideration when assessing the ranking, Dr Allibone said.
