Southern pygmy perch (Murray-Darling Basin lineage) is a little fish in big trouble. The species, once common in small, vegetated upland tributaries and permanent floodplain wetlands (e.g. wetlands in Barmah and Gunbower forests) throughout the Murray Corridor, is struggling. Over the past 40 or so years populations have severely declined due to altered flow regimes and lack of seasonal flooding of permanent wetlands; habitat loss and degradation, especially the loss of aquatic plants; and predation and competition with alien fish species such as carp and redfin perch.
Recent habitat modelling indicates that in the north central region of Victoria, there is a ~70% decrease in available southern pygmy perch habitat since European settlement. The percentage doesn’t consider the Millennium Drought which would have completely dried out many of the remaining suitable habitats.
New group formed to hunt wild pygs
The good news is that a dedicated group of people are working together to bring these great little fish back. A partnership formed between North Central Catchment Management Authority (CMA), City of Greater Bendigo Council, Native Fish Australia and The Australian and New Guinea Fishes Association to locate remnant populations of the species in the Campaspe, Loddon and Avoca catchments and start a captive breeding program. The group’s goal is to secure the species in the region and breed-up numbers to re-stock them into high quality ‘surrogate’ habitats (e.g. farm dams) and natural wetlands throughout its former range. The work was funded through a Department of Environment, Land, Water and Planning biodiversity on-ground grant.
In 2018, sampling was undertaken at sites where modelling results had indicated the species were likely to be found. Using bait traps and fyke nets set overnight, 33 sites were sampled yielding 451 southern pygmy perch individuals from 11 of the sites. Thankfully, four populations had survived the Millennium Drought: an abundant population was found in Pipers/Jews Harp Creek, a population in the upper Campaspe River, and two low abundance populations in McIvor Creek (upper Campaspe catchment) and Mountain and Middle Creeks (upper Avoca catchment). No pygmy perch were found in the Loddon catchment. Interestingly the sampling detected river blackfish at a site in the upper Campaspe catchment, where the species were thought to be extinct in the 1980s: an exciting find.
What the results showed
Fin clips were taken for genetic analyses to check that the pygmy perch populations originate from the Murray-Darling Basin (MDB) lineage and to determine the genetic diversity of the remnant populations. This work revealed that the Upper Campaspe population actually originated from the Bass lineage, south of the great divide. It’s thought that these fish may have come from the Maribyrnong river system, brought over the divide as fishing bait and subsequently released. This population was ruled out for captive breeding. All four populations had very low genetic diversity and evidence of inbreeding, so it was decided that the breeding strategy should involve mixing the MDB lineage populations for ‘genetic rescue’.
The group then set about collecting fish from three MDB lineage populations for captive breeding. Approximately 100 fish were collected and transported to a specialist pygmy perch breeder, Chris Lamin from Middle Creek Farms. After a salt bath to clear the fish of parasites, the brood stock was transitioned to a diet of black worms, getting them in good condition for spawning.
It is anticipated that the first batch of pygmy perch will be ready for release in to the wild in early 2020. The group is working towards releasing the fish in to custom built ‘frog ponds’ in the No 7 Reservoir park upper Bendigo creek catchment. This site will function as a backup population, a source population for the Bendigo creek, and an educational opportunity for visitors to the park. High quality natural wetlands in Gunbower Forest where the species used to occur prior to the Millennium Drought, have been selected for potential release.