Golden perch

Taxobox
name = Golden perch


image_caption = A large, stocked, female golden perch caught from an impoundment. The fishing lure is still in its mouth.
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Perciformes
familia = Percichthyidae
genus = "Macquaria"
species = "M. ambigua"
binomial = "Macquaria ambigua"
binomial_authority = (Richardson, 1845)The golden perch, "Macquaria ambigua", is an Australian native freshwater fish, primarily of the Murray-Darling river system.

The genus name for golden perch — "Macquaria" — derives from the Macquarie River where the first species in the genus was collected. The specific name for golden perch — "ambigua" — may derive from Latin form of the word 'ambiguous', which has connations of "two or more sides", and thus refer to the strong lateral compression (narrow, deep, flanks) adult golden perch display, or may refer to the confusion over where the original specimen ('holotype') was collected. (Richardson marked the specimen as having been collected from a marine environment.)

Description

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. Golden perch have an elongated deep body, laterally compressed, with a sizable mouth, small to moderate sized eyes and distinct curve to the forehead and "hump" above the head. 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).

Range

It is native primarily to lowland reaches of the Murray–Darling river system, but also push significant distances into upland reaches as well. In the Murray–Darling system golden perch are often found in sympatry ("together with") Murray cod, "Maccullochella peelii peelii".

The "Macquaria" perches, of which golden perch are one, continue the trend present in native fish genera of the Murray–Darling system of speciating into a lowland species and a specialist upland species. Golden perch, "Macquaria ambigua", are the lowland species while the closely related Macquarie perch, "Macquaria australasica", is the speciated, 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.

Like many Murray–Darling native fish, golden perch have crossed into eastern coastal river catchments through natural river capture events. Golden perch are found naturally in the Fitzroy–Dawson river in central Queensland and have also entered the internal Lake Eyre–Coopers Creek drainage system of Central Australia.

Both of these separate populations are likely to be separate species due to isolation from parent Murray–Darling populations, genetic drift and natural selection. The taxonomy of golden perch has not been updated to reflect this, although the term "Macquaria ambigua oriens", denoting sub-species status, has recently appeared in literature discussing the Fitzroy–Dawson population.

Reproduction and biology

Originally temperatures of close to 24 degrees Celsius were considered necessary for golden perch to spawn (Lake, 1967) but as with all Murray-Darling fish species it has become apparent that their "required" spawning temperature is flexible and that they can and do spawn at somewhat lower temperatures (as low as 20 degrees Celsius) (Koehn & Harrington, 2005). Golden perch have a flexible breeding strategy but "generally" need a spring or summer flood or "fresh" 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. Golden perch are highly fecund with egg counts frequently exceeding 500,000 AT A TIME. The eggs are generally planktonic, and hatch fairly quickly (24 to 36 hours) (Lake, 1967; Rowland, 1996).

Like other "Macquaria" species, sexual dimorphism is present, with females reaching much larger maximum sizes than males. Females also reach sexual maturity at older, larger sizes than males.

Golden perch continue the trend, among many native fish of southeast Australia, of being incredibly long-lived. Longevity is a survival strategy in the often challenging Australian environment which ensures that most adults participate in at least one exceptional spawning and recruitment event. These events are often linked to unusually wet "La Niña" years and may only every one or two decades. Maximum recorded age is 26 years (Mallen-Cooper & Stuart, 2003).

Diet

Golden perch are predators, taking yabbies, shrimp, frogs, small fish and aquatic invertebrates.

Conservation

Wild populations have declined significantly, especially in upper reaches of rivers, due to dams and weirs blocking migration, mitigating floods and freshes, regulating flows and releasing un-naturally cold water ("thermal pollution"), all of which interfere with migration, spawning and recruitment. Golden perch are extremely migratory and migration appears to have been important in maintaining populations in some reaches of river, usually the upper reaches.

Weirs are proving to be a more significant threat to golden perch than first thought, with a recent studying proving that about 90% of golden perch larvae passing through undershot weirs are killed (Baumgartner "et al.", 2006).

The species is however bred in hatcheries in large numbers and stocked. Concerns over genetic diversity issues are growing however.

References

* Baumgartner, L.J., Reynoldson, N. and Gilligan, D.M. (2006) Mortality of larval Murray cod ("Maccullochella peelii peelii") and golden perch ("Macquaria ambigua") associated with passage through two types of low-head weirs. "Marine and Freshwater Research" 57: 187–191
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* Koehn, J. D. & Harrington, D. J. (2005). Collection and distribution of early life stages of the Murray cod ("Maccullochella peelii peelii") in a regulated river. "Australian Journal of Zoology" 53: 137–144.
* Lake, J.S. (1967) Rearing experiments with five species of Australian freshwater fishes. I. Inducement to spawning. "Australian Journal of Marine and Freshwater Research" 18: 137–153.
* Mallen-Cooper, M. and I. G. Stuart (2003) Age, growth and non-flood recruitment of two potamodromous fishes in a large semi-arid/temperate river system. "River Research and Applications" 19: 697–719.
* Rowland, S. J. (1996) Development of techniques for the large-scale rearing of the larvae of the Australian freshwater fish golden perch, "Macquaria ambigua" (Richardson, 1845). "Marine and Freshwater Research" 47: 233–242

External links

* [http://www.nativefish.asn.au/golden.html Native Fish Australia - golden perch page]