Oxleyan pygmy perch

Common name: Oxleyan pygmy perch

Scientific name: Nannoperca oxleyana

Family: Nannopercidae

Conservation status: This species is listed as Vulnerable in Queensland (Nature Conservation Act 1992) and Endangered nationally (Environment Protection and Biodiversity Conservation Act 1999). It is ranked as a critical priority under the Department of Environment and Resource Management Back on Track species prioritisation framework.

Description

The Oxleyan pygmy perch is a small fish (approximately 5 cm in length) with a relatively large eye encircled with blue. Its body is usually light brown to olive in colour, darker on the back, mottled on the sides and has a distinctive round black spot with an orange border at the base of its tail fin. The fins are transparent for most of the year, with the anal fins turning black and tail fin scarlet when breeding.

Habitat and distribution

The Oxleyan pygmy perch prefers slow flowing or still waters. It appears only to be found in slightly acidic and tannin-stained water including swamps, streams and dune lakes that lie in the lowland, coastal 'wallum' heaths. It shelters near or within emergent vegetation or among the roots of riparian plants that grow into the water from undercut or vertical banks.

The Oxleyan pygmy perch has a restricted and patchy distribution that runs along the coast from Tin Can Bay, just north of the Noosa River drainage system to the Richmond River in northern New South Wales. It also occurs on Fraser, Moreton and Stradbroke islands. Its abundance within this area has been drastically reduced and it now only occurs as a number of isolated populations where there is suitable remaining habitat. It has been recorded in approximately twenty locations in south-east Queensland (Arthington 1996).

Life history and behaviour

There is little published information on the biology and ecology of the Oxleyan pygmy perch. The presence of some aquatic vegetation appears to be essential for this species survival as it is used for resting, shelter from predators, foraging, establishment and defence of territories by males, spawning, egg development and the growth of larvae and fry (NSW DPI 2005).

Oxleyan pygmy perch feed on freshwater crustaceans and insects and a small amount of algae and other plant material. They will forage along the stems of aquatic plants alone or in pairs, while younger fish move in groups of three or four. Their breeding season is from spring to autumn, but spawning mostly occurs in October to December. Spawning is thought to be stimulated by increasing water temperatures (minimum temperature 20^oC). The eggs adhere to underwater vegetationi this helps protect them from preadators and flowing waters. The young hatch in three to four days and start to forage in another day or two (Wager 1992).

Threatening processes

The Oxleyan pygmy perch has a limited geographic range that appears to have diminished over time because of habitat loss. Large areas of this species' coastal habitat have been cleared for residential development, forestry and agriculture. The slow-flowing water it prefers is also susceptible to nutrient enrichment and weed infestation. The geographical isolation of remaining populations, and the small size of the streams and swamps in which they live make these populations particularly vulnerable to habitat disturbance or chance events such as droughts (NSW DPI 2005).

Collection for the aquarium trade may also threaten some small, restircted populations of the Oxleyan pygmy perch. It is also likely that the introduced mosquito fish Gambusia holbrooki could out-compete the Oxleyan pygmy perch where the two co-exist. The mosquito fish is more likely to be found where the habitat has been disturbed (NSW DPI 2005).

Recovery actions

Rehabilitate creek habitats, for example through replanting native riparian vegetation and help provide greater protection to key areas of Oxleyan pygmy perch habitat.
Monitor populations of mosquito fish and other introduced non-native fish within or near populations of Oxleyan pygmy perch, and implement measures to reduce their impact.
Investigate and provide greater protection to key areas of Oxleyan pygmy perch habitat.
Identify Oxleyan pygmy perch habitat sites affected by sedimentation, pollution or barriers to fish movement such as roads and trails. Encourage land holders to control sediment and pollution and provide adequate fish passage.

What can you do to help this species

Never collect native fish from the wild.
Ensure that exotic fish (such as Gambusia) from home ponds and aquaria are not released into our wetlands and waterways.
Join a local landcare or waterways group and assist in revegetating or monitoring local creeks and 'wallum' habitats.

Further information

Allen, GR, Midgley, SH, Allen, M 2002. Field Guide to the Freshwater Fishes of Australia.CSIRO Publishing, Collingwood, Victoria.

Morris, SA, Pollard, DA, Gehrke, DA, and Pogonoski, JJ 2001. Threatened and Potentially Threatened Freshwater Fishes of Coastal New South Wales and the Murray-Darling Basin (PDF)*. New South Wales Fisheries, Sydney.

Wagner, R and Jackson, P 1993. The Action Plan for Australian Freshwater Fishes. Australian Nature Conservation Agency, Endangered Species Program, Project Number 147.

Reference

Arthington, AH 1996. Recovery plan for the Oxleyan pygmy perch Nannoperca oxleyana. Final Report to the Australian Nature Conservation Agency.

NSW DPI 2005. Oxleyan pygmy perch recovery plan and background paper, New South Wales Department of Primary Industries, Orange, NSW, Australia.

Wager, R 1992. The Oxleyan pygmy perch: maintaining breeding populations. Fishes of Sahul. 7(2): 310-312.

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Last updated 14 July 2011