Formerly in the genus Macquaria, recent genetic investigations have shown that this species (as well as Australian Bass) is not closely related to the other Macquaria species Macquarie or Golden perch. A medium-sized fish with a deep, laterally compressed body. Maximum length 750 mm (length to caudal fork: LCF) , maximum weight 10 kg; with fish >3kg uncommon. There is a single dorsal fin with a moderately deep notch between the spinous and soft-rayed portions. The pelvic fins are inserted behind the origin of the pectoral fins.
The back is generally dark grey and silvery, paling to whitish on the lower sides. The tail is forked, the eye is moderately large and the mouth is of moderate size with a protruding lower jaw. The dorsal head profile is slightly concave.
The Estuary perch predominantly lives in tidal or estuarine waters, but will penetrate significant distances upstream into fresh waters. It is a long-lived fish with a maximum age of 41 years recorded in the Bemm River in Vic.
A study on ageing found that most fish from the Hawkesbury and Clyde rivers were <10 years old and fish from the Bemm River were mostly 5-16 years old, with 65% of fish >12 years old. The length at age is highly variable between rivers with a 3-year-old fish from the Hawkesbury ranging from 160-290 mm LCF; an 8year old fish from the Clyde from 260 - 360 mm LCF and 16-year-old fish from the Bemm from 280-460 mm LCF. The 41-year-old fish was 400 mm LCF. Females grow larger than males.
Estuary perch breed in a range of salinities and estuarine habitats from seawater at the estuary entrance to near the upper end of the tidal limit. Peak spawning occurs from winter to late spring when water temperatures are from 14 to 19°C. Northern populations tend to breed earlier than southern populations. Males mature at ~220 mm length and females at 250-80 mm when both are in their fourth year. Fecundity is high and increases with fish length: a 340 mm fish has 182,000 eggs and a 400 mm fish 540,000. Average fecundity in the Hawkesbury, Clyde and Bemm rivers was 267,000. The eggs are 1.3–2.4 mm in diameter, round, non-adhesive and semi buoyant. They hatch in 2–3 days and the newly-hatched larvae are about 2.2 mm long.
The age structure of populations in the Clyde, Hawkesbury and Bemm rivers showed populations were dominated by a single age class, indicating variable recruitment success between years.
The species is an opportunistic carnivore, favouring mid-water prey such as shrimp and fish. The composition of the diet from freshwater environments in the Basin is unknown. However, a study of diet in both freshwater and estuarine habitats of the Hopkins River in Vic found that both large (>250 mm) and small (<250 mm) fish consumed mostly caddisfly larvae, and shrimp (Paratya) were the next most common item. In the estuary, large fish (>300 mm) fed mainly on fish, amphipods and shrimp, in descending order of importance, whereas small fish (<250 mm) fed mainly on shrimp and then amphipods. The diet varied seasonally, with terrestrial insects becoming prominent in November.
Apart from the adult migration downstream to estuaries to breed, little is known of movements. Hybridisation of estuary perch and Australian bass is known to occur in the wild, particularly in east Gippsland in Victoria.
Essentially a fish of coastal drainages from the Murray mouth in SA to the Richmond River in northern NSW, As its name indicates, it is an estuary dependent fish and is rare in the Basin, and recorded only from the Lower Murray, Lower Lakes (Alexandrina and Albert) and the Coorong. Specimens have been recorded in recent years from as far up the Murray as Swan Reach.
Estuary perch is in decline in several parts of its coastal range, as well as in the Lower Lakes and Coorong in the MDB. No individuals have been recorded from the Sustainable Rivers Audit (2004–2013) or the MDB Fish Survey (2014/15–2021/22).
Since the construction of the barrages and decline in river flows, the abundance of this species has fallen significantly in the Lower Lakes (Alexandrina and Albert). In coastal rivers, the propensity for the species to form large aggregations in estuaries for spawning or after floods exposes them to commercial fishing. The species range and abundance has declined in response to fishing pressure, flow regulation and Climate Change.
Allen et al. 2002; Harris & Rowland 1996; Howell et al. 2004; Koehn & O’Connor 1990; McCarragher & McKenzie 1986; Merrick & Schmida 1984; Near et al. 2012; Sim et al. 2000; Stoessel et al. 2018, 2019, 2021; Walsh et al. 2010, 2011, 2013; Wedderburn & Hammer 2003.
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