(For this reason, the species has proven difficult to breed artificially, as captive females do not produce ripe eggs when kept in still broodponds or tanks).

Macquarie perch appear to have inherited the sexual dimorphism of other Macquaria species where females reach a larger maximum size than males.

Macquarie perch were originally found in the larger upland rivers and streams in the south-eastern corner of the Murray-Darling system, which they usually co-inhabited with trout cod and one or both of the blackfish species.

Macquarie perch continue a pattern found in native freshwater fish of the Murray-Darling system of specialisation into lowland and upland stream inhabitants.

Recent evidence suggest the Shoalhaven population is now extinct after a rapid decline due to damming of their habitat and subsequent encroachment of legally and illegally stocked fish species.

[5] There is also a translocated self-sustaining breeding population of Macquarie Perch located in the middle and upper reaches of the Yarra River on the outskirts of Melbourne.

They highest numbers are found lowest reaches, which also support a mix of translocated native and introduced fish including trout.

Indeed, Macquarie perch populations have failed in significant stretches of relatively pristine upland river that offer excellent habitat, are not silted, dammed or overfished, and where there are no possible explanations for their demise except introduced trout species.

Recent research (Lintermans, 2006) records dietary overlaps that are significant by scientific criteria between Macquarie perch and introduced trout species.

Not only do these stockings threaten Macquarie perch by competition and predation, but rainbow trout fingerlings have been shown to carry significant levels of EHN virus.