Watchalunga Nature Reserve comprises approximately 92 hectares of low-lying wetland habitats, including areas of Fleurieu Peninsula swamp along the lower Finniss River, which is listed as a critically endangered ecological community. It is an important patch of remnant habitat containing highly significant South Australian biodiversity.
The millennium drought, 2022 floods and additional factors have led to an imbalance within freshwater networks connected to the River Murray, with an increase in alien fish species, such as Redfin and Common Carp, resulting in negative impacts on native fish species, both from predation by the larger invasive fish and habitat destruction.
Written article continues below video.
In the recent survey held in October 2025, alien fish species accounted for only 13.1% of the total catch, with 86.9% native fish, reflecting a significant improvement. Excitingly, this eighth survey also recorded a single Southern Pygmy Perch—the first observed since the 2020 survey—highlighting positive, ongoing recovery of the ecosystem.
Southern Pygmy Perch (Nannoperca australis) is a small (usually no more than 6.5cm long) freshwater native fish that is classed as Endangered in South Australia and is Protected. Native freshwater fish species play an important role in biodiversity in the ecosystems that Nature Foundation aim to restore across our reserve network.
In her report following the survey, Freshwater Ecologist, Dr Sylvia Zukowski from Nature Glenelg Trust (contracted by Nature Foundation to undertake this specialist work) recommended reintroducing this threatened fish species. This reintroduction was held in December 2025 and was undertaken by Sylvia and multiple members of the Nature Foundation team. This is the first native species reintroduction to be carried out at a Nature Foundation reserve.
Around 120 Southern Pygmy Perch were sourced from a nearby surrogate wetland where populations of threatened native fish are raised for reintroduction projects. The team added water from the Watchalunga wetland to the buckets and waited 15-20 minutes to monitor the fish as they acclimated. They then released them near the edges of the wetland, where they could find refuge in the reeds.
The species will be monitored in 2026 to assess their progress through the annual fish survey. We will also explore alternative ways to assess and assist the survival of the species which may include eDNA analysis, where water is sampled and analysed to detect DNA evidence of specific fish. This is a non-invasive technique for biodiversity monitoring and is particularly useful for small, secretive species.
We look forward to monitoring their progress and sharing the results with you.
Support our ongoing work through a conservation donation.