Macquarie perch

What it is

The Macquarie perch is a native Australian freshwater fish belonging to the family Percichthyidae. It shares its genus with the golden perch but differs significantly in habitat preference. The body is elongated, deep, and laterally compressed, featuring rounded caudal, anal, and soft dorsal fins, alongside a strong spiny dorsal fin. Adults typically measure between 30 and 40 centimetres, weighing 1.0 to 1.5 kilograms, with a maximum recorded size of 50 centimetres and 2.5 kilograms. Colouration ranges from tan to dark purplish-grey or black, often accompanied by distinctly silver irises. This species inhabits upland rivers and streams within south-eastern Australia.

Where it lives

Historically, this fish occupied larger upland rivers in the south-eastern corner of the Murray-Darling system. Genetic evidence suggests the ancestral population resides in the eastern coastal Shoalhaven River, which colonised the Hawkesbury-Nepean system approximately two million years ago. From there, populations moved into the Murray-Darling Basin around 657,000 years ago. Eastern coastal populations are smaller, averaging 15 to 20 centimetres, and possess one fewer vertebra than their Murray-Darling counterparts. The Shoalhaven population is likely extinct due to damming and introduced species. Translocated populations exist in the Mongarlowe River and the Yarra River near Melbourne, though these face varying levels of threat.

How it lives

This species exhibits a placid nature and feeds primarily on aquatic invertebrates such as caddisflies, stoneflies, and mayflies, supplemented by terrestrial insects. Sexual dimorphism is present, with females reaching larger sizes and older ages than males. Limited ageing studies record lifespans up to 20 years, potentially matching the golden perch at 26 years. Introduced brown and rainbow trout compete for the same dietary resources and prey on juveniles. The presence of the Epizootic Haemotopoeitic Necrosis virus, vectored by redfin perch, also impacts survival. Predation by trout occurs even in pristine habitats lacking other stressors, contributing to local declines.

Breeding and life cycle

Breeding biology is adapted to flowing upland waters, making artificial reproduction difficult as captive females rarely produce ripe eggs in still tanks. Spawning occurs in late spring when water temperatures reach 15 to 16 degrees Celsius. Fish lay demersal eggs over unsilted cobble and gravel substrates. These eggs sink into the spaces between stones, where they remain protected and incubate until hatching. This strategy mirrors that of introduced trout species. Successful reproduction requires specific flow conditions and substrate types not always available in regulated or altered river environments.

Fish and people

The Macquarie perch holds significance for sport fishing among enthusiasts familiar with Australian native species. However, it is not a primary food fish due to its endangered status and limited population numbers. Conservation efforts focus on protecting remaining habitats rather than commercial exploitation. Translocation programmes have attempted to establish populations in new waterways, such as the Yarra River, to safeguard genetic diversity. Anglers observe predation by introduced trout, highlighting the tension between recreational fishing interests and native species preservation. Cultural connections remain tied to its role as an indigenous component of south-eastern Australian river ecosystems.

Status and threats

Listed as endangered on state and Commonwealth listings, the Macquarie perch faces severe threats. Major causes include gross overfishing, habitat degradation through siltation, and flow regulation by dams. Thermal pollution from impoundments further stresses populations. The introduction of non-native trout species drives competition and predation, while redfin perch vector fatal viral diseases. Many remaining populations are in extinction vortices, with some coastal groups already lost. Government agencies have been slow to breed the species in significant numbers, and occasional stocking of trout into native habitats exacerbates decline. Protection measures require strict habitat management and removal of invasive competitors.

Relatives and look-alikes

The closest relative is the golden perch, which occupies lowland habitats and serves as a less specialised ancestor. Both share the genus Macquaria and similar physical traits, though the golden perch is more adaptable. Trout cod and blackfish species historically co-inhabited the same upland streams. Introduced brown and rainbow trout pose significant ecological threats through dietary overlap and juvenile predation. Redfin perch act as vectors for diseases affecting Macquarie perch survival. Understanding these relationships highlights the complex interactions between native fauna and introduced species in altered river systems.

Questions people ask about Macquarie perch

Good reading and sources

• Macquarie perch on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data