A medium sized fish with a deep, laterally compressed body. Maximum length ~550 mm and maximum weight 3.6 kg; usually <400 mm and 1 kg. Body colour is generally black-grey or bluish grey, and some individuals are distinctly mottled, particularly small juveniles. The tail is rounded, the eye is large and white, and there are prominent pores on the snout and around the eyes. The mouth is large and the jaws equal in length.
There are three cryptic species contained within Macquarie perch, one of which occurs in the Murray–Darling, and one in eastern or coastal rivers (the Hawkesbury-Nepean and Shoalhaven systems). A third species from the Kangaroo River in the Shoalhaven system is thought to have recently become extinct. More is known of the ecology of the Murray–Darling species than the coastal one, although many aspects of their ecology are similar. Males reach sexual maturity at 2 years of age and ~210 mm total length, and females at 3 years and 300 mm. Maximum known age is 30 years, and in one reservoir population 25% of fish were 15-30 years old. In the Cotter River, males mature at about 140–150 mm and in Lake Dartmouth ripe males have been recorded down to lengths of 117 mm. Spawning occurs from October to December, with spawning commencing when water temperature rise to ~16 °C, with fish from lakes moving into tributaries to spawn. However, not all populations move upstream to spawn, with recent studies on the Yarra and Murrumbidgee rivers showing little spawning movement occurred, or that movement could also be downstream. The spawning sites are located at the foot of pools and in riffles with eggs drifting downstream to lodge amongst gravel and cobble. Hatching usually occurs after 10–11 days at water temperatures of 15–17°C, (but may be quicker at higher temperatures) with newly hatched larvae ~7 mm long. Macquarie perch appear particularly choosy about spawning sites, with most eggs coming from relatively few sites in any particular year. High flows during and following the spawning season reduce successful recruitment of young-of-year (YOY) fish, probably through disturbance of eggs at spawning sites or damage to larvae. For example, high flows in late Nov-Dec 2021 resulted in almost total failure of YOY recruitment in the upper Murrumbidgee. Radio-tracking studies have shown that adult and sub-adult fish are largely crepuscular and nocturnal and occupy well-defined homesites during the day. Macquarie perch is preyed upon by a variety of species including alien species (trout) and birds such as cormorants and darters. A single Great cormorant from Cotter Reservoir contained six Macquarie perch, with individuals 100–275 mm detected in cormorant stomachs. A quiet and docile species, Macquarie perch feed on shrimps and small benthic aquatic insect larvae, particularly mayflies, caddisflies and midges, but in lakes cladocerans can also be a significant dietary item.
Originally described from 3 specimens collected near Bathurst on the Macquarie River, the species was extinct in this drainage until a small stocking of 7,500 into Winburndale Rivulet and Dam in 2021. The Murray–Darling species is currently typically found in the cool, upper reaches of the Murray–Darling Basin in Vic, NSW and the ACT. Historically it was present in more lowland habitats such as the Murray River between Euston and Tocumwal and the Edwards River and Barmah Lakes near Deniliquin. It is now extinct in these locations and in SA but is still known to exist in the upper reaches of the Murrumbidgee, Lachlan and Murray catchments in NSW; the Goulburn, Broken, Ovens and Mitta Mitta catchments in Vic; and the Cotter and Murrumbidgee rivers in the ACT.
Some stream populations were severely affected by the Millennium Drought. The species has been stocked or translocated into a number of reservoirs including Talbingo, Winburndale Cataract, Khancoban, Expedition Pass, Lake William Hovell and Coliban reservoirs, and stocked/translocated into streams including the Mannus, Mongarlowe, Retreat, Paddys, upper Murrumbidgee, upper Cotter, Queanbeyan, Yarra, Goulburn, Yea, Ovens, Buffalo, and Wannon rivers, Winburndale Rivulet and Hollands, Sevens and Adjungbilly creeks. The populations of Macquarie perch in Dartmouth and Eildon reservoirs and Lake Burrinjuck initially supported significant recreational fisheries but all have declined dramatically, with the species now virtually absent from Eildon and Burrinjuck. The Dartmouth population recovered noticeably following the Millennium Drought. Most remaining populations are small and isolated, although populations in the upper Murrumbidgee and Goulburn river systems and Dartmouth are locally abundant. The larg- est remaining populations are in Dartmouth (Vic), the upper Murrumbidgee River (NSW), and Cotter River (ACT), with good, translocated populations in Cataract Reservoir and Yarra River outside the MDB. Most populations have reduced genetic diversity. Only 33 individuals were recorded from the Sustainable Rivers Audit (2004–2013) across 4 river valleys, with 25 in montane, 6 in upland, 1 in slopes and 1 in lowland elevational zones. 131 individuals have been captured from 6 river valleys in the MDB Fish Survey (2014/15–2021/22) with 68 from the Murrumbidgee and 46 from the Mitta Mitta valleys.
Threats include the continued spread and interactions with alien species such as trout, Redfin perch and Carp; exposure to Epizootic Haematopoietic Necrosis Virus (carried by Redfin perch); infection with the parasitic copepod Lernaea cyprinacea; habitat modification including sedimentation, clearing of riparian vegetation, construction of dams and weirs (barriers to migration and recolonisation), cold-water discharges from dams which prevent successful breeding; and low genetic diversity (a result of population fragmentation and isolation). Climate change will increase frequency and severity of bushfires with rainfall following the 2019-20 bushfires resulting in catastrophic sedimentation that severely impacted several populations across NSW, Vic and ACT.
ACT Government 2018; Broadhurst et al. 2013, 2016, 2019; Cadwallader 1981; Cadwallader & Eden 1979; Cadwallader & Rogan 1977; Douglas 2002; Ebner et al. 2007a; Faulks et al. 2010; Gilligan 2005a; Gilligan et al. 2010b; Ingram et al. 2000; Koehn et al. 2020a; Koster & Crook 2017; Koster et al. 2014b; Lintermans 2013a; 2016, 2021, 2022b,c; Lintermans & Ebner 2010; Lintermans et al. 2011, 2014, 2015, 2019b; Lutz et al. 2021, 2022; Pavlova et al. 2017; Pearce 2013; Pearce et al. 2021; Piggott et al. 2021; Shelley et al. 2021; Silva et al. 2018; Stocks et al. 2020; Thiem et al. 2013; Todd & Lintermans 2015; Tonkin et al. 2010, 2014a, 2016, 2017a, 2019a; Trueman 2011; Wharton 1973; M. Lintermans unpubl. data.
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