The olive perchlet was once found throughout NSW, but now the small fish is considered threatened across the state.
It is an important species in the Murray-Darling Basin, acting as a food source for bigger fish and birds while helping control mosquito populations.
"The olive perchlet feed on the larvae from the mosquitoes," central west NSW local Russell Spencer told AAP.
"They've been living here for millions of years and now they're just about wiped out."
Aquatic habitat degradation is impacting Australia's freshwater fish populations, with more than 30 per cent threatened with extinction.
In the Murray-Darling Basin, more than half its native fish species are under threat.
Mr Spencer remembers growing up on the river, fishing with his grandfather who passed down traditional knowledge and stories about the local waterways and their inhabitants.
As an adult, the Wiradjuri man's passion for fish manifested in his long-term volunteering through the NSW Department of Primary Industry's Fishcare program.
Waterways must be cared properly for to keep any fish population thriving, Mr Spencer said.
The olive perchlet requires natural billabongs with an abundance of aquatic vegetation for their habitats.
But these are difficult to find across the Murray-Darling Basin in NSW, according to conservation charity Ozfish.
Light does not penetrate the water which has become murkier, while introduced species like carp 'rip up' aquatic vegetation, says Sean Graham, team leader of OzFish's Dubbo river repair bus.
Mr Graham has a plan to revitalise olive perchlet numbers in the Murray-Darling Basin.
"We've come up with what we hope is an innovative solution, a kind of bypass where we can float the aquatic vegetation on the top of wetlands using rafts," he said.
"If you bring the plants up toward the top, it should do fine if you float it on a raft and it's also going to be safer from carp up there toward the surface."
Mr Graham has been working to make the rafts with the Boys to the Bush program, which focuses on mentoring and connecting young men.
Building the rafts is a joy for program participant Beau.
"I love working with my hands and helping improve our local environment," he said.
"Sean makes it fun and teaches us what we need to do, then we have a go."
It's a "no-brainer" to get as many people as possible engaged in restoring the waterways, Wiradjuri Cultural and Environmental Ranger Group founder Peter White said.
"The more people who get involved and bring all that knowledge and get it into this arena, to get together and work on it, the better," he said.
