Silver Perch

Silver perch (Bidyanus bidyanus) are relatively easy to obtain and are considered a good angling and table species. They are somewhat similar to golden perch in appearance and usually require about two years or more to reach a harvestable size. They feed on a much wider range of items than golden perch, and their diet usually includes some plant and algal material. A mix of both silver perch and golden perch in a dam is often more productive than either species by itself. The recommended initial stocking rate for silver perch is 250 fish per hectare. Silver perch are unlikely to breed in a farm dam.

The Silver Perch is a moderately elongate fish with a small head and small scales. Colouration varies with water conditions. Adults are often silver-grey with darker scale margins but they can be greenish, brown or golden. The belly is white and the median fins are grey. The pelvic fins are usually white.

This species grows to 40 cm in length and 8 kg in weight, however 30 cm and 1.5 kg individuals are more commonly seen.

The Silver Perch is endemic to Australia. It occurs naturally in freshwaters throughout much of the Murray-Darling Drainage of Queensland, New South Wales, Victoria and South Australia. It has been introduced into the Lake Eyre Basin and coastal river systems of south-eastern Queensland, New South Wales and south-western Western Australia. It prefers fast-flowing waters but is also known from rivers, lakes and reservoirs.

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.

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.