Threatened Fishes of the World: Macquaria australasica Cuvier, 1830 (Percichthyidae)

Abstract

Common names: Macquarie perch, white-eye, silver-eye, mountain perch, bream. Conservation status: Endangered (ANZECC 1999). Identification: D VIII–XII, I + 11–14, A III + 8–11, P 14–17, V I + 5, LL 42–60, gill rakers 17–21, vertebrae 28–31. Moderate-sized percoid fish (max. 460 mm, 3.5 kg), almost black or dark silvery grey to light or off-white silvery grey in colour, eye large, jaws equal (Harris & Rowland 1996). The species status is unresolved since investigations indicate that there are putatively two species (‘eastern’ and ‘western’) of Macquarie perch separated by the Great Dividing Range and possibly two sub-species within the ‘eastern’ species. Distribution: Formally widespread throughout the more southerly tributaries of the Murray-Darling River system of south-east Australia, as well as the Hawkesbury and Shoalhaven River systems on the eastern seaboard (Cadwallader 1981, Harris & Rowland 1996). Current distribution is fragmented and only small discrete populations remain. ‘Western’ populations are restricted to the upper reaches of some tributaries of the Murray-Darling River system, in particular, the Mitta Mitta River system above Darmouth Dam, the Goulburn, Murrumbidgee and Lachlan river systems, and one translocated population in the Yarra River. ‘Eastern’ populations are confined to the Shoalhaven and Hawkesbury river systems (Ingram et al. 1990, Harris & Rowland 1996). Abundance: No reliable population estimates exist for either the ‘eastern’ or ‘western’ forms. Habitat and ecology: Macquarie perch occupy a range of habitats from riffle and boulder areas in relatively small upland streams to larger deeper rivers with sand and clay substrates and submerged timber and snags as well as impounded waters. Their diet includes aquatic invertebrates, especially insects and crustaceans. Reproduction: Spawning, which occurs in shallow upland streams, is apparently triggered by increasing daylength and water temperatures and occurs in October to late December when temperatures range between 14◦C and 18◦C. Spawning Macquarie perch (‘western’ form) are oviparous and the demersal and slightly adhesive eggs (2.0–4.0 mm in diameter) appear to be shed into the water upstream of riffle areas. Hatching commences approximately five days after fertilisation and continues for up to six days (at water temperatures of 18–20◦C). Newly-hatched embryos are approximately 4.5–6.5 mm in length. Feeding commences on zooplankton about 3–5 days after hatching is completed (Gooley 1986, Ingram et al. 1994). Threats: A general degradation of the riverine environment caused by a number of contributing factors including modifications to rivers for hydro-electric, flood mitigation and irrigation schemes, increased pollution from domestic, agricultural and industrial sources, sedimentation, over-fishing, and impacts of introduced species, such as competition, predation and spread of disease (Cadwallader 1978, Ingram et al. 1990). Conservation action: Total bans on the capture of Macquarie perch exist in the Australian Capital Territory (ACT) and New South Wales (NSW). The capture, keeping and trading of Macquarie perch is controlled by legislation in Victoria. Captive breeding programs have been undertaken at government fish hatcheries in NSW and Victoria to produce and release juveniles of the ‘western’ form into selected sites within its former range to re-establish natural populations (Gooley 1986, Ingram et al. 1990). However, these programs have ceased due to difficulties associated with inducing spawning in both captive broodfish and mature fish in spawning condition captured from the wild. Between 1986 and 1997 approximately 456 000 juveniles were released into nine sites throughout the Murray-Darling basin. Early results indicate survival at some of these sites only. Attempts to re-establish populations of the ‘western’ form by translocation of mature fish have occurred in Victoria, New South Wales and the Australian Capital Territory (ACT Government 1999) with mixed success (Lintermans 2000). Conservation recommendations: Improve state and federal legislation to further protect Macquarie perch and preserve and rehabilitate riverine habitats where both existing and re-introduced (stocked) populations occur. Much basic biological information still needs to be collected for both ‘eastern’ and ‘western’ forms including resolution of species status, habitat requirements, life history patterns in the wild and surveys of existing populations to determine size, distribution and breeding status. Remarks: Since the status of Macquarie perch was upgraded to endangered, fisheries regulations have increased the level of protection from recreational fishing in Victoria, and a three year project has been instigated to investigate the Lake Dartmouth population.