LITTLE GALAXIAS AND YARRA PYGMY PERCH FOUND IN BARWON

Corangamite Catchment Management Authority (CMA) and Ecology Australia completed targeted aquatic fauna surveys in autumn this year, searching for two rare fish species in the upper Barwon catchment: little galaxias Galaxiella toourtkoourt and Yarra pygmy perch Nannoperca obscura. The two freshwater species are listed as 'endangered' and 'vulnerable' respectively under the Victorian Flora and Fauna Guarantee Act 1988 and the surveys aimed to ascertain the current distribution and status of the species in the catchment.

Surveys were conducted at 21 historic and newly selected sites in the Upper Barwon Flagship Program area. This included the east Barwon and west Barwon River branches, and Dewings Creek (the Upper Barwon Flagship), together with a number of smaller tributaries including Pennyroyal Creek, Gosling Creek, and Matthews Creek.

Yarra pygmy perch and little galaxias have previously been recorded within the upper Barwon catchment during surveys between 2000 and 2013, however no monitoring of either species has been completed for over a decade. Environmental DNA (eDNA) sampling recorded little galaxias in both the east and west branches of the Barwon River in 2018 and 2024 respectively. Unfortunately eDNA provides no information on the health or abundance of these species in these waterways. Importantly, little galaxias are known from only two isolated locations in the east Barwon River and upper Gosling Creek catchment. Surveys were designed to detect movements of these species that may have resulted from three years of above average rainfall.

A combination of fyke nets, bait traps and backpack electrofishing was used to detect the species at these locations. All species were measured and returned to the point of capture during survey. Some genetic samples of little galaxias were taken at a select number of sites to improve our knowledge of the genetic diversity of these populations. A total of 37 little galaxias were captured across six sites, confirming the continued presence of the species at three previously recorded sites, in addition to three new locations. Two new sites were in close proximity to previously recorded sites, while the third new location represented the first recording of little galaxias at Pennyroyal Creek. Little galaxias were not detected at two sites where previous records exist. A total of 36 Yarra pygmy perch were captured at a single site on Pennyroyal creek – the only known historical site for the Upper Barwon Flagship Program area. Little galaxias were not detected at the two additional survey sites on the Barwon River west branch.

This study confirmed the continued presence of the threatened little galaxias and Yarra pygmy perch species in the upper Barwon catchment, although only one population of Yarra pygmy perch is currently known to persist. Additionally, although little galaxias were detected at six sites, many were in close proximity and are likely only sub-populations, meaning that there are essentially only two known populations of little galaxias confirmed in the catchment. Detecting little galaxias in Pennyroyal Creek is a first for the catchment. Further survey may be required to ascertain the abundance of this species as only one individual at this site was recorded. The small number of populations and confirmed sites (i.e. sub-populations) makes both species highly vulnerable to extirpation (becoming regionally extinct) in these catchments in the absence of appropriate and ongoing management.

Ongoing monitoring of both species is recommended along with a program of sensitive habitat restoration where these species persist. Consequently, the focus of the ongoing program of works in the upper Barwon catchment seeks to address the reach of the east Barwon River where the little galaxias reside. In collaboration with relevant landholders we propose to secure these known locations from further degradation and support these refuge populations of EPBC listed fauna in the Upper Barwon Flagship area.

View the full report from Ecology Australia.