Silver perch - aquaculture prospects


The silver perch (Bidyanus bidyanus) is a native freshwater fish. Its natural distribution extends through the western drainage of New South Wales, including most of the Murray-Darling Basin. It is a dark gray colour along the top, changing to silvery on the sides and lower areas, and has a small mouth.

Biology of silver perch

Silver perch inhabit a multitude of environments within its natural range, encompassing the cool clear waters of the upper reaches and highlands, to the lower turbid slow flowing rivers of the west. It is an omnivorous species, with a diet including insects, small crustaceans and vegetation. Silver perch are known to grow up to 6kg, however, specimens over 3kg are rare. Habitat destruction and fishing pressure has caused natural populations to decline drastically.

Silver perch spawn naturally in response to a change in conditions; usually a rise in water levels (rainfall) coinciding with water temperatures above 23° C. Each female will lay up to approximately 160,000 eggs, which hatch within 36 hours. After about 5 days, the yolk sacs have been absorbed and the larvae commence feeding on zoo plankton.

NSW industry status

Silver perch was recognised as a good candidate for aquaculture as far back as 1916, however, it was not until 1965 that NSW DPI began research into this species. In the 1970's the Narranderra Fisheries Research Station began research on the hormone induced spawning of perch, and this technology was made available to industry in the early 1980's. Since that time, a thriving hatchery industry has existed based on the hatchery production of silver perch and other native species.

During the early 1990's, scientists at the Grafton Aquaculture Centre began research into the grow-out production of silver perch in ponds. This technology has since been utilised by private growers and the commercial production of silver perch is now developing into an industry, with  increases in each production year since 1994. For the production figures see the NSW DPI aquaculture production reports.

Growth and production

Most of the research into silver perch production has focused on pond based culture, however, some farmers are currently experimenting with intensive recirculation tank system farming for the over-wintering of fingerlings.

Fingerlings that have been weaned onto a commercial diet are readily available from a number of hatcheries in NSW. Once quarantined and settled, fingerlings are ready for stocking. NSW DPI recommends the use of a nursery phase prior to stocking into grow-out ponds. After approximately 9 months, fingerlings should be harvested from nursery ponds, counted, graded and then restocked into grow-out pond, depending on their size category. Research data has shown that silver perch can be successfully grown at stocking densities of up to 20,000 fish/ha.

The optimum temperature range for commercial production is 23-28° C.  In a good growing climate, silver perch can be raised to market size of 600-800g in around 18 months.

Silver perch can utilise low protein diets based on plant & meatmeal proteins. Most feeds available have a protein content of around 35%.  Commercial feeds for silver perch are available in pellet form, with either sinking or floating properties. Food conversion ratios (FCR's) for silver perch are generally in the range of 1.3-2:1 (kg of food: weight growth), often depending on the farmers experience and husbandry practices.

Water exchanges in intensive silver perch farms may at time be necessary. Ponds will also need regular topping up to account for evaporation and seepage. As such access to large volumes of good quality water is required, NSW DPI recommends a water budget of at least 40ML/ha/yr for all silver perch farms.


Silver perch has a number of biological characteristics that make it highly suited to intensive culture. These include its ability to be raised in high densities, general hardiness and high survival (>90%), rapid and uniform growth (2/fish/day), willingness to accept artificial feeds, availability of fingerlings, its non-cannibalistic nature, high meat recovery (40%), excellent eating qualities, and its ability to utilise a number of natural food sources (omnivorous).

Silver perch usually show a large size variation during the fingerlings stage. At the completion of this stage, they must be graded into the grow-out ponds.

Site selection and system design

When choosing a suitable site for the pond culture of silver perch, the following should be taken into account:

  • Above the 1/100 year flood height on the eastern drainage and not inundated by a 1/100 year flood on the western drainage
  • Adequate buffer zone from the nearest waterway (at least 50m)
  • Soil with appropriate water holding capabilities (high clay composition) and free from residual pesticides and contaminants
  • Areas free of acid-sulphate soils and high water table
  • Access to suitable good quality water (at least 40ML/ha/yr)
  • Suitable climate for the culture of silver perch
  • Close to markets and infrastructure.

To ensure that silver perch aquaculture industry develops in an environmentally and economically sustainable manner, NSW DPI has developed a policy to regulate the licensing of silver perch farms. This policy sets out specific criteria (design and operation) that the proposed operation must meet before an aquaculture permit will be issued. Proponents applying for a permit should ensure their operation complies with the policy criteria before submission of applications (see 'Aquaculture Permits for Silver Perch').

Water quality

Silver perch are a freshwater species. However, they are quite hardy and can tolerate a range of water quality parameters. Intensive ponds can at time be volatile with respect to water quality, and rapid changes could mean the difference between healthy fish and high mortalities.

As a general rule stocking densities should not exceed 20,000 fish/ha. Less experienced farmers should begin with lower stocking densities until they have the experience to manage heavily stocked ponds. Dissolved oxygen levels above 3mg/L and free ammonia levels of less than 0.1mg/L should be maintained.

Poor water quality can result in lowered growth rates and increased susceptibility to infection by disease agents. To assist in maintaining water quality at an acceptable rate, regular monitoring of water is required. THe farmer can adjust aeration, water exchange, feedings and stocking levels to maintain optimum water quality.

Diseases and parasites

Infection with disease and parasites is a response by fish to stresses occurring in their environment. The most common of these would be deterioration of water quality, and over-crowding. Most pathogens and parasites occur naturally in ponds and natural aquatic environments.  Once fish become stressed however, opportunity for the disease to infect increases via the lowering of the fish's immunity defenses.  Stressors include handling, poor water quality, crowding, predation or poor nutrition.

Regular monitoring for disease is essential when understanding intensive perch culture.


Most of the silver perch currently produced is sold for the live fish trade in Sydney's Asian restaurants. They are presented in glass tanks allowing patrons to select the fish they wish to dine on.

Silver perch has been readily accepted into this market, with farmers receiving strong prices ($7-10/kg live) at the farm gate. The very nature of the live fish market requires fish to be 600-800g in weight and have a good physical appearance. Fish not suitable for the live trade is usually sold whole chilled on the Sydney Fish Market auction floor. Some live and chilled product is sold at the Brisbane and Melbourne Fish markets, with small amounts sold regionally.

Export markets for silver perch are still relatively unexplored, with the potential domestic markets not yet fully realised. Local markets appear to be relatively unfulfilled, and some researchers predict that silver perch has the basis to form an industry capable of producing over 10,000 tonnes/annum. There may also be future potential to supplement some of the $500 million worth of fish imported into Australia every year, predominantly in the form of cheap, processed/frozen, white flesh fillets e.g. hoki and hake. However perch production costs would have to decrease significantly to compete as imported fish retails for $4-5/kg.

Like most freshwater fish  silver perch can develop a muddy flavour. This occurs as a result of fatty tissues in the fish absorbing compounds released by blue green algae in the culture ponds. The only way to remove the off-flavour is by purging in clean water for 3-21 days, depending on the water temperature.

Further information

For further information, call NSW DPI:

Port Stephens Fisheries Centre: 02 4916 3900
Grafton: 02 6640 1600

Copies of licensing and policy requirements for silver perch may be obtained from here. Further information on the farming of silver perch can also be obtained from the following references:


Rowland, S and Bryant, C (eds) (1994). Silver Perch Culture - Proceedings of Silver Perch Aquaculture Workshops, Grafton and Narrandera, April 1994. Austasia Aquaculture Publication.

Rowland, S (1998). 'Silver Perch'. The New Rural Industries - A Handbook for Farmers and Investors.