Golden Perch

Golden perch are medium-sized fish, commonly 30–40 cm and 1–2 kg in rivers. Fish from rivers are smaller and somewhat streamlined — fish in man-made impoundments are much deeper-bodied and show much greater average and maximum sizes. In rivers, has been recorded to 9 kg, in impoundments to 15 kg. A 24-kg fish caught from Kow Swamp, Victoria in the early 1900s, and labelled and sold as a "Murray perch", is often referred to as the largest recorded golden perch, but this record is doubtful — this record grossly exceeds all other size records for golden perch, and the specimen in question is far more likely to have been a Murray cod (Maccullochella peelii), which grow to far larger sizes than golden perch. Golden perch have an elongated, deep but laterally compressed body, with a sizeable mouth, small to moderate-sized eyes, a distinct curve to the forehead, and a distinct "hump" above the head. The opercula or gill covers possess a small, flat spine sharp enough to cut unwary fishermen's fingers. The caudal fin, soft dorsal fin, and anal fin are rounded. The spiny dorsal fin is short to moderate in length and strong. Golden perch vary from in colour from pale silvery-gold (turbid waters) to deep yellow/gold or bronze-black (very clear waters).

Golden perch are native primarily to lowland reaches of the Murray–Darling River system, but also extend far into slope habitats and occasionally even lower upland reaches. In the Murray–Darling system golden perch are often found in sympatry with Murray cod. The Macquaria perches, of which golden perch are one, continue the trend present in Murray–Darling native fish genera of diversification into more generalist lowland species and more specialist upland species. Golden perch, M. ambigua, represent the lowland species, while the closely related Macquarie perch, M. australasica, is the more specialised upland species which used to inhabit the upland reaches of the southern Murray–Darling basin, although this endangered species has now been almost wholly displaced by introduced trout species, dams, and associated effects such as cold-water pollution, and habitat degradation/modification. Like many Murray–Darling native fish, golden perch have crossed river catchments through natural river capture/connection events. Golden perch are found naturally in the Fitzroy–Dawson River in central Queensland and the internal Lake Eyre–Cooper Creek drainage system of Central Australia. The fish has also been successfully introduced to other river systems in the Northern Territory, Queensland, and New South Wales, confusing studies of the natural range. …

In the Murray River, wild male golden perch generally reach sexual maturity at 3 years of age and 32.5 cm in length, and wild female golden perch at 4 years of age and 40 cm in length. The latter fact is a concern given that minimum size limits for the species are currently less than 40 cm, at 30 cm. Originally, temperatures close to 24 °C were considered necessary for golden perch to spawn, but as with all Murray-Darling fish species, multiple field studies have shown that their "required" spawning temperature is flexible and that they can and do spawn at lower temperatures. In the Barmah Forests region of the Murray River, for instance, fertilised drifting golden perch eggs have been netted in water temperatures as low as 16.9 degrees Celsius (full range 16.9 to 24.7 degrees). Golden perch have a flexible breeding strategy but generally (but not always) require a spring or summer flood or "fresh" (temporary, within-channel increase in flow) to stimulate spawning. Like some other primarily lowland native fish species of the Murray–Darling river system, these floods or freshes appear to be necessary for good survival and recruitment of spawned fish. …