Macquarie Perch (Macquaria australasica)
Macquarie Perch. Photo: E. Beaton, ACT Government
The native Macquarie Perch (Macquaria australasica) was listed as an endangered species in the ACT in 1997 and risks becoming extinct in the Territory unless active steps are taken to protect and improve its habitat. It is listed as endangered nationally and by NSW and Victoria. It is extinct in South Australia.
Related to freshwater bass and cod, the Macquarie Perch is known for its humped back, large white eyes and rounded tail. Fish rarely get larger than 40 centimetres and heavier than 1 kilogram.
Once broadly distributed, Macquarie Perch are now only found in the cooler, upper reaches of the Murray–Darling River system. In the ACT, there are three natural populations—in the Murrumbidgee, lower Paddys and Cotter rivers—and some translocated individuals in parts of the Upper Cotter, Molonglo and Paddys rivers. Translocation has had mixed success. Macquarie Perch is now only found rarely in the ACT Murrumbidgee River.
Cool, shaded and pristine streams and rivers are the perfect habitat for the Macquarie Perch, which are most active between dusk and dawn. They will travel up to a kilometre a day to feed on shrimp, insect larvae, yabbies, zooplankton and molluscs.
Macquarie Perch can live for more than 20 years, though most live less than 15. During late spring and early summer, the fish migrate to spawning spots. Females deposit eggs at the foot of pools, head of riffles or fast-flowing sections of river, where males fertilise them. The eggs then wash downstream and lodge in gravel or rocky areas until hatching.
Conservation threats
The major threats to Macquarie Perch are habitat destruction or modification, river regulation, barriers to fish passage, alien fish species, effects of wildfires, reduced genetic diversity, increased predation particularly from cormorants, reduction in spawning habitat availability and climate change
Sedimentation is a major problem because it has filled pools, smothered spawning sites and reduced light penetration, impacting on the fish’s environment and food. Land clearing and weeds have particularly impacted the Lower Cotter and Murrumbidgee catchments. Dams have altered natural flow patterns threatening riverine species.
Alien fish such as Rainbow Trout, Brown Trout, Carp, Redfin Perch and Eastern Gambusia compete with native fish for food and habitat. They can also eat the native fish, introduce and spread parasites and contribute to habitat degradation.
Fish are highly vulnerable to the impacts of climate change. Macquarie Perch use temperature to initiate spawning and increased temperatures may alter breeding cycles. The predicted increase in summer storms and frequency of bushfires could also damage eggs.
Like many Macquarie Perch populations across the nation, the Cotter Reservoir and upper Murrumbidgee River populations have reduced genetic diversity, most likely because there is little connectivity between populations and/or small numbers of founding fish. This means the fish are less robust and more prone to extinction.
Conservation actions
The ACT Government proposes to maintain, in the long term, a viable, wild population the Macquarie Perch through the Macquarie Perch Action Plan (2018) and the ACT Aquatic and Riparian Conservation Strategy (2018).
Conservation actions that have already been introduced:
- Environmental flows for the Cotter River to maintain populations and special flows prior to the breeding season to help spawning success
- Fishing for the species has been prohibited
- Annual monitoring of populations takes place to inform management decisions for the species
- Rehabilitation of the Upper Murrumbidgee Demonstration Reach (UMDR), which stretches from Bredbo to Casuarina Sands and aims to improve fish habitat
- Rehabilitation of population connectivity by construction fishways along the Cotter River
- Research and management related to the construction of the enlarged Cotter Dam.
A genetic rescue (using translocation from other populations) project is taking place to help the species and aims to improve the fitness and evolutionary potential of the area’s Macquarie Perch by reducing genetic isolation, increasing genetic variation and reducing inbreeding.
The action plan outlines how we can:
- protect sites in the ACT where the species occurs
- manage habitat to conserve existing populations and establish or re-establish new populations
- manage aquatic habitats, alien fish species, connectivity, spawning site access, stream flows and sedimentation in existing habitats and adjacent habitat to increase habitat area and connect populations.
- enhance genetic diversity of Cotter Catchment populations
- improve understanding of the species’ ecology, habitat and threats
- improve community awareness and support for Macquarie Perch and freshwater fish conservation.
More information
- Macquarie Perch Action Plan, 2018
- Aquatic and Riparian Conservation Strategy, 2018
- Australian Government Macquarie Perch Conservation Advice
Contact
Email environment@act.gov.au or phone Access Canberra on 13 22 81.