A tiny native freshwater fish species is one giant step closer to being saved from extinction thanks to a 15-year effort by a group of committed ecologists.

Yarra pygmy perch (Nannoperca obscura) – which grow to just 4 centimetres in length – were decimated by the effects of the Millennium Drought and by 2008, their numbers had fallen to critical levels. Alarmed by the situation, a group of aquatic ecologists banded together to workout a way to secure the future for the species.

The group began saving the last remaining fish from the river to breed in surrogate dams on private properties around the Adelaide Hills, Barossa and Fleurieu regions. The surrogate breeding dams now have enough fish for successful and sustainable wild reintroductions. Finding suitable surrogate dams is a hard task, with dams needing to meet strict criteria to qualify. Luckily, landholders have been amazing in offering their dams and working with scientists to make this program a success. One of the critical needs of a surrogate dam is the inclusion of aquatic vegetation, and the majority of dams surveyed did not have this. Nature Glenelg Trust received a grant from the Murray Darling Basin Authority through the Native Fish Recovery Strategy to establish aquatic vegetation at three wetlands which are now all used as important surrogate sites for Yarra pygmy perch.

Using fish from the surrogate sites,round 9,000 Yarra pygmy perch were released into the Murray River at 3 sites near Hindmarsh Island (part of the Lower Lakes, Coorong and Murray Mouth Ramsar site) in the summer of 2023-24. Another 7,000 fish have since been released over the summer of 2024-25, in an attempt to re-establish the species back into the wild.

Recent efforts have included the use of soft release structures which are submerged in the river to allow the fish to acclimatise for 2 weeks before being fully released into the river. Site monitoring in early February 2025 resulted in 17 Yarra pygmy perch being recaptured, before being released back into the wild.

The long-term effort to rescue the small remaining population of Yarra pygmy perch is a fantastic example of what can be achieved through collaboration between government, NGOs, universities, Traditional Owners and committed individuals. Yarra pygmy perch were first detected at Hindmarsh Island in 2002 but were known to inhabit areas of south-eastern Australia since the late 19^th century. Preferring still or slow-moving waters, the species thrives in areas with aquatic vegetation which provides protection, food and breeding habitat.

Efforts to save the Yarra pygmy perch have been led through a partnership between Nature Glenelg Trust, the Murraylands and Riverland Landscape Board and the Landscape Hills and Fleurieu, with support from the Big Little Four working group, the University of Adelaide, Flinders University, the Department of Environment and Water and the Ngarrindjeri Aboriginal Corporation.

Funding for this project was via the Murraylands and Riverland Landscape Board and Hills and Fleurieu Landscape Board Landscape levies, and funding from the MDBA through the Native Fish Recovery Strategy: Tri-State Murray NRM Alliance Recovery Reach Program.