An Australian senior scientist on Wednesday unveiled he has discovered 16 additional species of galaxiids, which are small, scaleless freshwater fish found in mountain streams.

According to Tarmo Raadik, from the Department of Sustainability and Environment's Arthur Rylah Institute, before the discovery the environmentalists and scientists were thought only one species, the Mountain Galaxias, existed in Australia.

However, Raadik found the populations in isolated areas in mountain river streams, with eleven additional species were identified in state Victoria and five in state New South Wales of Australia.

Raadik said the fish, which measure about 10cm to 15cm in length, are found in small isolated populations.

"Because of that, they are under threat," Raadik told Australia Associated Press on Wednesday. "If you have more wildfire or drought, they can eliminate these small isolated populations."

Raadik said the species would likely be listed as threatened, and therefore plans would be needed for their conservation.

Raadik said most of the species look the same and this is why the variations had not be discovered earlier. Raadik has used genetic techniques to confirm the different species.

Galaxiids were found only in the southern hemisphere, in Australia, South America, New Zealand and South Africa.