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A look at Macquarie Perch by Simon Kaminskas & Jim Tait


ACT - Endangered, Protected
NSW - Vulnerable, Protected
VIC - Endangered Though limited take allowed from some populations
National - Endangered, listed under the EPBC Act

Click for larger picture of Macquarie Perch
Click on image for larger version
Picture courtesy - Jim Tait



Macquarie Perch (Macquaria australasica) are medium sized (~2.5 kg max) native fish found in the Murray-Darling system. They are in the Macquaria genus that also contains Golden Perch, Australian Bass and Estuary Perch, and they are closely related to Golden Perch. Macquarie Perch reflect a pattern present in several other Murray-Darling native fish of speciating into upland species and lowland species, Macquarie Perch being the upland species and their relative the Golden Perch being the lowland species. Macquarie Perch used to be caught regularly by anglers using bait and artificials including Trout anglers using fly gear. They were renowned as a strong and exciting sportfish and an excellent table fish. They are now totally protected in most states, though some Victorian populations including one translocated to the Yarra still form part of a recreational fishery.

Distribution and Habitat
As the term "upland" suggests, Macquarie Perch are primarily a species of the larger sub-alpine rivers and streams in the SE corner of the Murray-Darling system. Due to the broad temperature tolerances all native fish possess, Macquarie Perch where occasionally recorded from the lowland reaches of the Murray River and southern tributaries in previous decades. However Macquarie Perch have an upper temperature limit of 26 degrees and their primary habitat is the cool, clear, flowing upland rivers and streams now generally considered prime Trout habitat.

Macquarie Perch Distribution
Macquarie Perch Distribution. Click on map for larger version.

Age and Spawning
Macquarie Perch like most native fish are long-lived fish. Extreme longevity is a survival strategy for native fish in our harsh environment, as they survive many years to capitalise on exceptional conditions for spawning and recruitment, when those conditions occur. There is some uncertainly about their maximum age, but their close relative the Golden Perch regularly reaches ages of 20 years, with a maximum recorded age of 26 years and Macquarie Perch may reach similar ages.

Murray-Darling Macquarie Perch have a maximum size of approximately 50 cm and 2.5 kg but fish over 2kg are rare. A more common size for Murray-Darling Macquarie Perch is 0.5 - 1.5 kg. Like the other species in the Macquaria genus female Macquarie Perch grow much larger than male Macquarie Perch and all large Macquarie Perch are females.

Macquarie Perch spawn in November or December, when water temperatures reach 15 or 16 degrees. The fecundity of Macquarie Perch is surprisingly low compared to their relative the Golden Perch, with a reported egg count of 32,000 eggs per kilogram of fish weight (i.e. 1.0 kg fish, 32,000 eggs, 2.0 kg fish 64,000 eggs). Spawning takes place at the head or tail of pools with strongly flowing water and clean gravel or cobble. The male fertilises the eggs with a cloud of milt as the female sheds them. The eggs sink into gaps and cracks in the gravel or cobble where they are protected until they hatch. Eggs are reported to take 13 - 18 days to hatch depending on temperature.

Diet and Feeding
Macquarie Perch are not as aggressive predators as Murray Cod, Trout Cod and Golden Perch. While they will occasionally take small fish, they are generally aquatic insect eaters. Aquatic insect larvae such as mayfly, caddisfly and dragonfly larvae make up the bulk of their diet, with a small amount of terrestrial insects also taken. Studies have shown that there is a very strong overlap between the diet of the introduced Trout species and Macquarie Perch.

Status and Causes of Decline
The main causes of decline are habitat destruction (particularly siltation), overfishing, competition and predation by introduced Trout species, altered flow and temperatures associated with reservoirs, and possibly disease.

Habitat Destruction
Catchment clearing, grazing pressure, associated soil erosion, destruction of riparian (river-bank) vegetation, and the trampling of river banks by domestic stock has led to severe siltation of rivers and streams throughout the Murray-Darling Basin. Like many larger native predatory fish Macquarie Perch are reliant on deep unsilted pools as their main habitat. Macquarie Perch also rely on clean and unsilted gravel and cobble in flowing areas for spawning sites. Severe siltation can destroy both of these critical areas. The branches and leaves of native riparian vegetation contributed to upland rivers and streams are a critical part of the food chain. Destruction of riparian vegetation results in impacts to the food chain and food resources for fish in these habitats.

Macquarie Perch, whether in impoundments or in undammed rivers, will make strong upstream migrations in late spring or early summer prior to spawning. There have been shocking slaughters of Macquarie Perch in the early 1900s by fishermen using both lines and nets in tributaries of Eildon Dam including the Goulburn River. Catches exceeding several tons from one pool in one day have been recorded. (Macquarie Perch populations in Eildon Dam have long since collapsed). In more recent times anglers have exploited the spawning run of Macquarie Perch in Dartmouth Dam (now in the process of collapsing for various reasons), and illegal netters jeopardise remnant Macquarie Perch populations in several rivers with set nets that exploit the Macquarie Perch's upstream migrations.

Introduced Trout species
Introduced Trout species also significantly impact on Macquarie Perch, and the Trout Cod often found with Macquarie Perch in upland rivers and streams.

Trout prey heavily on small fish of any species and cause mortality of juvenile Macquarie Perch. (NSW Fisheries literature states that Trout are "known to prey on juvenile Macquarie Perch and Trout Cod"). With a significantly higher egg count Macquarie Perch have survived this impact better than Trout Cod, and have managed to hang on in a few Trout dominated upland rivers/streams. Many of these populations are now collapsing, suggesting that over the longer term Macquarie Perch do not survive well in upland rivers/streams holding introduced Trout.

Trout also compete heavily with Macquarie Perch at all sizes, juvenile and adult, for food resources, feeding sites and habitat. Studies have shown that there is a very strong overlap between the diet of the introduced Trout species and Macquarie Perch.

It is not known how much cryptic mortality there may be with juvenile Macquarie Perch from predation by adult Trout or from intense competition for food and shelter from juvenile Trout. Saturation stockings of Trout are likely to be particularly damaging in this regard.

Murray Darling Basin Macquarie Perch have no Trout-free habitats. Introduced Trout species are found in every single larger upland river and stream in the Murray-Darling system, which were the primary habitat for Macquarie Perch.

From a species conservation perspective there is a strong case for removing introduced Trout from some large upland rivers/streams to create upland native fish reserves and re-establishing Macquarie Perch and other vulnerable natives such as Trout Cod in these rivers/streams. Unique catch-and-release fisheries could be another aim of these areas.

Altered flow and temperatures from reservoirs
Dams have a devastating effect on all native fish species including Macquarie Perch for the same reasons. Dams replace the seasonally varying temperature regime in a natural upland river with an artificial uniformly frigid temperature regime due to low level (deepwater) outlet releases. This interferes with cues for roe development and spawning, interferes with actual spawning, and reduces survival and growth of juvenile native fish. In extreme cases rivers or streams are too cold for native fish to even live in, though this is not such a problem with the cold-adapted Macquarie perch. Contrary to popular belief, such an artificial frigid temperature regime will also usually (depending on the exact stretch of river) lead to an impoverished invertebrate population and therefore reduced food resources for fish. Dams also reduce the height of flood flow peaks experienced in downstream reaches which are important for flushing out accumulated silt and 'resetting' instream habitat conditions.

The EHN virus is a virus carried by the introduced Redfin Perch. Research suggests EHN virus was a dormant "native" virus without a host until Redfin Perch were introduced in the 1860s. Research has proven that it readily infects Macquarie Perch which have an almost 100% fatality rate. Anecdotally it has been noted that as redfin expand into areas inhabited by Macquarie Perch their populations often undergo major reductions (i.e. lower Murrumbidgee). Fortunately overlap between Macquarie Perch and Redfin Perch is largely limited to impoundments as Redfin Perch dislike fast flowing river environments which remain the primary strong hold for Macquarie Perch. In some instances fish passage barriers have also been beneficial for halting the spread of redfin in Macquarie Perch habitats. Of more concern is research that has shown EHN virus is present in a significant proportion of Rainbow Trout fingerlings produced in Australia. Rainbow Trout stockings into remnant Macquarie Perch habitat may not just be threatening Macquarie Perch through competition and predation but also through the introduction of EHN virus.

Other Macquarie Perch species
Naturally occurring Macquarie Perch populations are also found in the coastal Hawkesbury-Nepean and Shoalhaven river systems. These coastal populations of Macquarie Perch are the result of an ancient "river capture" events where eastern coastal catchments have cut westwards into inland drainages. Research has shown there are now significant taxonomic and genetic differences between these coastal Macquarie Perch and Murray-Darling Macquarie Perch, and suggesting that the coastal Macquarie Perch are now a separate species.

Coastal Macquarie Perch appear to inhabit the upper reaches of these coastal river systems upstream of the main Bass-holding areas. They exhibit a far smaller maximum size than Murray-Darling Macquarie Perch of around 15 - 18 centimetres.

The situation with the coastal Macquarie Perch species has been confused by at least two translocations of Murray-Darling species Macquarie Perch into these coastal catchments. Coastal Macquarie Perch are reported as being abundant in some areas of the two coastal systems in which they occur - the conservation situation with these species may not be as critical as with the Murray-Darling species.

The future?
Macquarie Perch have largely been forsaken by those that previously loved them (including rec fishers) and are sliding closer to extinction every day. While recovery plans are being initiated at a commonwealth and state (NSW) level, no Fisheries Department is breeding them, and major knowledge gaps and problems remain for the successful artificial breeding and recovery of Macquarie Perch. One of the key challenges is that Macquarie Perch do not respond to artificial hormone induction techniques used successfully to breed many other native fish. They appear to require 'natural' stream flow conditions to 'roe up' and the development of dedicated facilities with constructed flow chambers may provide one option.

Due to the limited wild populations of Macquarie Perch remaining, the production of fingerlings is critically important and could support several key initiatives including:

1. Research - particularly on the susceptibility of fish to EHN virus and also on competitive interactions with trout

2. Conservation stocking into suitable habitat where the species has been lost or numbers have become critically low

3. Establishment of a limited recreational fishery by stocking into selected impoundments.

Although option 3, establishment of limited recreational fishery is currently a much lower priority than conservation and research needs, limited recreational fisher access in stocked impoundments as has been done for other endangered species (i.e. the Mary River Cod in Queensland) would serve to reintroduce recreational fishers to the species and garnish their support for further investment in the full rehabilitation of the species.

If recreational fishers (in NSW, ACT, Vic) are keen to see this species rehabilitated they should write to their relevant State ministers seeking increased investment in the rehabilitation of Macquarie Perch, particularly the development of successful artificial breeding techniques. Full recovery of the species could see this once popular recreational species re-established as a recreational target in streams as well as impoundments. Without such concerted efforts the future does not look positive for Macquarie Perch.

Further Reading
Dept of Environment & Water Resouces

Copyright© 2004 Simon Kaminskas & Jim Tait. Sweetwater Fishing Australia