Macquarie perch

Taxobox
name = Macquarie perch
status = DD
status_system = iucn2.3

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image_width = 240px
image_caption = This exceptionally large Macquarie perch was caught on a lure (visible in the picture) and was carefully released.
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Perciformes
familia = Percichthyidae
genus = "Macquaria"
species = "M. australasica"
binomial = "Macquaria australasica"
binomial_authority = Cuvier in Cuvier and Valenciennes, 1830

The Macquarie perch ("Macquaria australasica") is an Australian native freshwater fish of the Murray-Darling river system. It is a member of the Percichthyidae family and is closely related to the golden perch ("Macquaria ambigua").

The Macquarie perch derives its scientific name from the Macquarie River where the first scientifically described specimen was collected ("Macquaria") and a derivation of the Latin word for "southern" ("australasica").

Description and diet

Macquarie perch are a medium sized fish, commonly 30–40 cm and 1.0–1.5 kg. Maximum size is about 2.5 kg and 50 cm. Their body is elongated, deep, and laterally compressed. The caudal fin, anal fin and soft dorsal fin are rounded. Spiny dorsal fin medium height and strong. Mouth and eyes are relatively small. Colouration can vary from tan to (more commonly) dark purplish-grey to black. The irises of the eyes are distinctly silver.

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.

Breeding and biology

The Macquarie perch is 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. The demersal (sinking) eggs fall into the interstices (spaces) between the gravel and cobble, where they lodge and are then protected and incubated until hatching. This is a breeding strategy similar to that used by introduced species of trout.

Macquarie perch appear to have inherited the sexual dimorphism of other "Macquaria" species where females reach a larger maximum size than males. Females also reach sexual at older, larger sizes than males.

Maximum ages for Macquarie perch are not clear but it is possible they are similar to their relative the golden perch (maximum age 26 years). The extremely limited work done on ageing Macquarie perch has only recorded fish to around 11 years of age so far.

Range

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. Macquarie perch are a speciated, more specialised upland version of the golden perch, which is "primarily" a lowland fish. (Having said this, the "primarily" lowland golden perch, being highly adaptable species, still extend a significant distance into upland habitats).

Macquarie perch, like many other Murray-Darling native fish, have managed to cross the Great Dividing Range into eastern coastal systems through natural river capture events. They are found in the eastern coastal Shoalhaven and Hawkesbury-Nepean river systems. Although the situation has been blurred with translocations of Murray-Darling fish into these eastern coastal systems, it appears that, as with other naturally occurring populations of Murray-Darling native fish in eastern coastal systems, these Macquarie perch are almost certainly separate species due to isolation from parent populations, genetic drift and selective forces. The taxonomy for Macquarie perch has not been updated to reflect this. Major differences between the eastern coastal species and the Murray-Darling species are that the eastern coastal species displays a far smaller average and maximum size (15 and 20 cm respectively) and are reported to have one less vertebra than the Murray-Darling species. Recent evidence suggest the Shoalhaven species may be close to or at extinction due to damming of their habitat and subsequent encroachment of legally and illegally stocked fish species. The Hawkesbury-Nepean species appears to be threatened by introduced trout and other exotic fish, river damming and regulation, siltation, and urban encroachment, but does not appear to be as critically threatened as the Murray-Darling species. Information on this page relates primarily to the Murray-Darling species.

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. In this stretch however no fish species is particularly dominant, and introduced trout are not numerous.

Conservation

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. Dietary studies have documented significant overlap between the diet of Macquarie perch and introduced trout species, and anglers have observed predation of Macquarie perch juveniles by introduced trout species. Several publications in the 1940s through to the 1960s by the director of the Victorian Fisheries and Game Department (A.D.Butcher) documents predation on juvenile trout cod, Macquarie perch and other upland native fish species by introduced trout species, and major dietary overlaps. Recent research (Lintermans, 2006) records dietary overlaps that are significant by scientific criteria between Macquarie perch and introduced trout species.

Over the last 20 or 30 years, the last few remaining Macquarie perch populations in upland habitats have faltered. All of these populations appear to be in extinction vortices and may disappear completely over the next couple of decades.

Macquarie perch have proved difficult but not impossible to breed. However, no Australian government agency is breeding Macquarie perch, and some government agencies are irresponsibly stocking upland habitats containing remnant Macquarie perch populations with 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.

Saving Macquarie perch is also complicated by the fly-fishing lobby groups in Australia that pursue introduced trout, with their vociferous and ill-informed denials of the impacts of introduced trout on Macquarie perch and other native upland fauna. Fishery Departments appear reluctant to address the issue and confront these lobby groups. Indeed, Fishery Departments' priority have long been the introduced trout species, and they have long neglected our native fish species, with the result that research and detailed knowledge on most native fish species is scant, and some native fish species find themselves in the endangered state that Macquarie perch are now in.

A full examination of the history of Macquarie perch will inescapably conclude that a few sizeable upland rivers and streams in the southern Murray-Darling system will need to be made trout-free, and then seeded and/or restocked with Macquarie perch, if this native fish is to survive. The evidence clearly shows this species cannot survive in the long term in most upland rivers and streams holding introduced trout species . Such a measure will also be needed to save the endangered trout cod ("Maccullochella macquariensis"), a more speciated upland version of the Murray cod ("Maccullochella peelii peelii") and a species that was often found in sympatry (together) with Macquarie perch in larger upland rivers and streams.

Macquarie perch were originally a frequent capture by anglers fishing larger upland rivers and streams of the southern Murray-Darling system, including on flies and fly-fishing gear meant for introduced trout species, and were renowned as a strong and thrilling sportsfish. Perhaps this may be their salvation. Anglers, including fly-fishermen, may support the removal of introduced trout species and the "return" of a few upland river habitats to Macquarie perch if they are guaranteed angling access after strong populations have re-established, and thus have unique new native fisheries to look forward to.

External links

* [http://www.sweetwaterfishing.com.au/MacquariePerch.htm Sweetwater Fishing Australia - Macquarie Perch]
* [http://www.nativefish.asn.au/maccas.html Native Fish Australia - Macquarie perch page]

References

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* Butcher, A.D. 1945. The food of indigenous and non-indigenous freshwater fish in Victoria, with special reference to [introduced] trout. "Fisheries Pamphlet 2". Fisheries and Wildlife Department, Victoria.
* Butcher, A.D. 1967. A changing aquatic fauna in a changing environment. "IUCN Publications, New Series" 9: 197–218.
* Cadwallader, P.L. (ed.) 1977. J.O. Langtry's 1949–50 Murray River Investigations. Fisheries and Wildlife Paper. Ministry for Conservation, Victoria.
* Cadwallader, P.L. 1981. Past and present distributions and translocations of the Macquarie perch "Macquaria australasica" (Pisces: Percichthyidae), with particular reference to Victoria. "Proceedings of the Royal Society of Victoria" 93: 23–30.
* Cadwallader, P.L. & Eden, A.K. 1979. Observations on the food of Macquarie Perch, Macquaria australasica (Pisces: Percicthyidae) in Victoria, "Australian Journal of Marine and Freshwater Research" 30: 401–409.
* Cadwallader, P.L. & Rogan, P.L. 1977. The Macquarie Perch, "Macquaria australasica" (Pisces: Percicthyidae), of Lake Eildon, "Australian Journal of Ecology" 2: 409–418
* McDowall, R.M. (ed.) 1996. "Freshwater Fishes of south-eastern Australia." Reed Books, Sydney, Australia.
* Lintermans, M. (2006) The re-establishment of endangered Macquarie Perch Macquaria australasica in the Queanbeyan River, New South Wales, with an examination of dietary overlap with alien trout. Technical report, CRCFE, Canberra.
* McKeown, K.C. 1934. Notes on the food of trout and Macquarie Perch in Australia, "Records of the Australian Museum" 19: 141–152.
* Merrick, J.R. & Schmida, G.E. 1984. "Australian freshwater fishes: biology and management." Griffin Press, Sydney, Australia.
* Rhodes, J.O. 1999. "Heads and Tales: Recollections of a Fisheries and Wildlife Officer." The Australian Deer Research Foundation Ltd, Melbourne.
* Trueman, W. and Luker, C. 1992. Fishing Yesteryear. "Freshwater Fishing Australia Magazine" 17: 34–38.
* http://www.fishnet.com.au/default.aspx?id=225