Macquarie perch

The ray-finned fish

Macquarie perch is a ray-finned fish in the family Percichthyidae (order Perciformes) — Macquaria australasica.

Range and habitat

Macquarie perch were originally found in the larger upland rivers and streams in the south-eastern corner of the Murray-Darling system, that 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. Macquarie perch are a speciated, more specialised upland version of the golden perch, that is primarily a lowland fish. (Having said this, the primarily lowland golden perch, being highly adaptable species, did extend into upland habitats) in some situations.

Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.

Diet and breeding

Macquarie perch are a relatively placid native fish species with the bulk of their diet consisting of aquatic invertebrates such as caddisfly, stonefly and mayfly species, with a small quantity of terrestrial insects taken as well. The Macquarie perch is primarily an upland native fish and has a breeding biology clearly adapted to flowing upland rivers and streams. (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 breed in late spring at temperatures of 15 to 16 °C, in flowing water over unsilted cobble and gravel substrate.

In crisis

Murray-Darling Macquarie perch are now listed as endangered on state and Commonwealth listings. Gross overfishing by anglers, habitat degradation through siltation, and regulation of flow and "thermal pollution" by dams have all been major causes of decline. A mysterious but endemic disease called Epizootic Haemotopoeitic Necrosis virus (EHN virus), now vectored by introduced redfin perch, has been proven to be fatal to Macquarie perch, and may have contributed to the decline of some populations of Macquarie perch in upland impoundments.

What has become clear however is that total domination of the Macquarie perch's upland habitats by introduced brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) have also been a major cause of decline. 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.

Macquarie perch is Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.

Sources

Written for this catalog from the English Wikipedia article on Macquarie perch, Wikidata item Q3100700. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.