Rare fish believed to be extinct north of Margaret River found in Perth Hills

A research trial has led to a surprise discovery of a rare fish in the Perth Hills previously thought to be extinct north of Margaret River.

Three years ago, members of the Bibbul Ngarma Aboriginal Association (BNAA) undertook eDNA sampling as part of their BoorYul-Bah-Bilya program to assess and restore the health of the Mandoon Bilya (Helena River).

The team expected to find a lot of information through the testing – eDNA detects the species present in an area through the DNA left behind in the environment – but they never imagined they’d come across Balston’s pygmy perch.

BNAA executive director and environmental scientist Francesca Flynn told WAtoday it took a while to confirm the eDNA sample was correct, but a recent survey with the Department of Water and Environmental Regulation left no doubt the fish was alive – and thriving.

“We went out recently with [DWER] and surveyed a lot of sites along that river, and it was there, in the area where the eDNA said it would be,” she said.

“It was amazing to see. We were all really excited. It was really special to know that little fish has survived, and it’s there in the Perth Hills.”

The team found 13 fish during the 24-hour survey.

BNAA BoorYul-Bah-Bilya ranger Trei Winmar was one of the team members who helped find the pygmy perch and said it was a “really great opportunity.”

“We have only just started as BoorYul-Bah-Bilya Rangers, so to have already found this fish has been great timing for us. Not many people get to see this fish, so it was amazing to be there and be part of the discovery,” he said.

“Hopefully, it will lead to us doing more of this kind of work – getting out on Country, discovering what’s still out there, and learning how we can better protect our rivers.”

Balston’s pygmy perch was understood to live across much of the South West region, but was long believed to have disappeared from most rivers and wetlands north of Margaret River.

The small fish typically grow to about 6cm in size and live in thick reeds along the edge of a river.

The fish species was located in the upper catchment above the Mundaring Weir and Flynn said she believes it’s because of the location that the fish were able to survive after all these years.

“What it means is that the river is, which we knew anyway, resilient and strong and special,” she said.

“As a drinking water source, it has been far better protected than other rivers in the southwest, many of which have been impacted by clearing, agriculture and mining.”

This discovery is not the first for the BNAA team. In 2024, the group found a new quokka population in the Perth Hills.

Famously associated with Wadjemup (Rottnest Island) the quokka populations are also known to exist in the South West and Great Southern’s forests; however, numbers have declined over the years.

“This was another win for eDNA as it helped us confirm another locally extinct species that was thought to be long gone from this area,” Flynn said.

“We have a fauna monitoring program to understand the health of the river catchment and one day an unexpected animal showed up on the images.

“We were all excited, but there was some debate about what the animal was. Most of us thought it was a quokka, but one volunteer was adamant it was a woylie. We sampled some of the scat from the camera area and eDNA testing confirmed it was quokkas.”

Flynn said the quokkas live along the creek lines in the similar spots the pygmy perch was found.

“There are more out there than you think,” she said.

“We’ve never seen a quokka out in the bush, they’re very well hidden, but they’re definitely out there.”

Flynn hopes the two discoveries can help bring better protection for the catchment area and the Helena River as a whole.

“These discoveries are incredibly significant, but ultimately, we hope they lead to better protection of this area, greater recognition that the Mandoon Bilya is a very special river, and also a lot more effort and resources devoted to understanding how this little fish and the quokkas have survived here for so long,” she said.