Growing and harvesting silver perch

Successful silver perch farming is a function of stocking rate, water quality, diet and stock management. In well-managed dams, production of 5–10t per hectare is attainable.

Growout

Stocking rates

Growers usually purchase fingerlings and produce fish to market size (500g) in 10–12 months or even less.

To prevent excessive size variation at harvest and inefficient feeding rates, farmers usually divide growout into two stages:

• Stocking rates at the fingerling (nursery) stage range from 20,000 to 100,000 fish per hectare.
• After about 9 months, fingerlings can be harvested from nursery ponds, counted, graded and then restocked into growout ponds at 5000–21,000 fish per hectare.

The higher stocking rates require careful monitoring of the pond environment to avoid mass mortality.

Feeding

Silver perch are omnivores, consuming zooplankton, small crustaceans, aquatic insects, molluscs, algae and plant material. Juvenile silver perch preferentially feed on crustaceans and zooplankton with the proportion of algae and plant material increasing with age.

Both fingerlings and adult silver perch readily accept artificial diets, which they are generally fed in pellet form. Pellet size varies with the size of the animal. The optimum dietary protein level is between 32% and 36%. Along with protein, silver perch also require an artificial diet with sufficient lipids, carbohydrates, vitamins and minerals for energy and growth.

The food conversion ratio (FCR) ranges from 1.2:1 for fingerlings to 1.5:1 for growout. That is, it takes 1.2–1.5kg of food to produce 1kg wet weight of fish.

Harvesting

Harvesting techniques include total drain harvesting and the use of seine nets for partial harvests. Harvesting methods are dictated by the amount of product required and pond management needs.

Off flavours are normally removed by finishing the fish in clean water for 5–10 days before they are marketed. The addition of salt (sodium chloride) is recommended for this purpose.

Also consider...

• You will need to discuss technical and licensing aspects of any proposed aquaculture venture with staff from Fisheries Queensland and the Department of Environment and Science before proceeding with site selection, design and, where applicable, land purchase.
• Download the latest report to farmers for aquaculture industry statistics and production data.