Some 22 native freshwater fish have a 50/50 chance or worse of becoming extinct within two decades unless targeted action is taken to save them, according to new research. The most threatened fish is Victoria’s tiger-striped shaw galaxias which, experts concluded, had an 80% chance of being gone in 20 years time. Nineteen of the 22 fish identified in the study, carried out through the federal government’s national environmental science program, are not listed nationally as threatened. “These are the most threatened and those that will go extinct unless we do more,” said Mark Lintermans, an associate professor at the University of Canberra and a freshwater scientist who led the research, titled Big Trouble for Little Fish. He said about half of the species on the list had only been officially described in the scientific literature in the past 10 years. Seven have not been formally described. “These species are only just being recognised, but they are already threatened,” he told Guardian Australia. The list emerged from workshops where 15 experts were asked to estimate the threats to species across all of Australia’s 315 different groups of freshwater fish. Then experts were asked to rank the chances of those fish surviving, given what was known about their plight and the current management regimes in place. All of the assessments were carried out before the 2019 and 2020 bushfires that also impacted Australia’s rivers. One species at risk, the yalmy galaxia from the Snowy River National Park, was thought to have about 2,500 individuals left before the fires. But a post-bushfire field survey, Lintermans said, could find only two individuals – one male and one female. The species was now “extremely close to extinction” he said. Ten of the 22 are found in Victoria, five in Queensland, four in New South Wales, two in Western Australia and one species from Tasmania. All but one of the fish are less than 15cm long. Lintermans said species that had never been scientifically recognised had probably already been lost. “We have certainly lost species before we knew we had them,” he said. “But they all play a role in their ecosystem and they are likely to be the top predator, and they regulate all the bugs. Some are keystone species.” Many species had been pushed to the brink by invasion of alien fish species, Lintermans said, either accidentally by fishing practices or deliberately, for example with the release of non-native fish into waterways from home aquariums. The shaw galaxias, which are present only in a tributary of the Caledonia River in Victoria’s coastal Gippsland region, had seen a 99% cut in numbers in the past 10 years after an invasion of trout. Only about 80 individuals are thought to remain. Alongside the shaw galaxias, the other most at risk species were Daintree rainbowfish, barrow cave gudgeon, red-finned blue-eye, little pygmy perch and stocky galaxias. Work on the list started at the Australian Society for Fish Biology, where a longer list of 90 species had been generated through research. Many of the fish now exist in only isolated pockets. One on the list, for example, the Bloomfield River cod, lives in only a small stretch of the Bloomfield River in far north Queensland isolated by waterfalls. Lintermans said climate change was now an emerging threat to many of the species, which had been isolated in small areas of river that tended to be at the upper range of the temperatures that the fish could tolerate. Getting the species properly described in the academic literature and getting them on threatened species lists was a vital step, he said. Freshwater native fish, especially the smaller ones, tended to be overlooked and forgotten, but they needed a national action plan in place to protect them. “It’s hard for governments to prioritise to conserve things if they don’t recognise what they have got. Describing a species is that first step,” he said. Lintermans said he was personally determined that “we don’t lose things on my watch” and that he wanted his grandchildren and their children to be able to go out and see those fish in rivers and streams.