| | Growout Phase Techniques for the extensive and semi-intensive cultivation of silver perch have been developed in NSW over the past decade. Silver perch can be reared with success (90 per cent survival) in various systems from unmanaged, undrainable farm dams to purpose built semi-intensive pond systems (Rowland et al., 1995; Rowland, 1995a): - Extensive farming in a farm dam involves minimum input from the farmer - fish are stocked at a rate of around 350 per hectare and fend for themselves;
- Semi-intensive farming in a farm dam requires limited management to maintain fish and possibly polyculture with crustaceans. Some feeding may occur and fish may be caged within enclosure;
- Semi-intensive pond production usually involves purpose-built ponds for fish farming at a specific size, volume and depth. It may also include predator control, water quality maintenance and regular feeding; and
- Intensive farming using raceways, ponds with regular controlled water exchange or cage culture systems, is generally characterised by complete artificial feeding, usually with optimised diets (pellets), well-managed aerated ponds with water exchange and an increased labour requirement. Stocking is intensive and may vary from 7,000 to 40,000 fish per hectare, with an optimum rate around 20,000/ha (Rowland, 1995b).
Silver perch growout ponds should be built no larger than 0.25ha, with aeration provided to achieve high yields (Figures 2 & 3) (Rowland, 1995b).  | | Figure 2: Paddle Wheel Aerator |
 | | Figure 3: Cross section of a typical fish pond |
The table below provides a summary of the various parameters considered necessary for silver perch aquaculture. It is critical that any site being considered for commercial silver perch aquaculture satisfies these basic requirements. | Parameter | Suitable range | Measurement frequency | Comments | | Temperature | 22-28 o C (optimum) | 2-3/week | Favourable range for growth, silver perch survive in 10-32 o C. | | Salinity | < 5 g/L | 1/month | Have been reported to survive at higher salinities. | | Dissolved oxygen | > 3.0 mg/L | 2-3/week | | | pH | 7-9.5 | 2-3/week | Water should be well buffered. | | Total alkalinity | 50-150 mg/L | 1/year | Buffering capacity of the water. | | Ammonia | < 0.1 mg/L total NH 3 | 2-3/week | NH 3 toxicity increases with increasing pH (increasing alkalinity) and temperature. | | Turbidity | < 20,000 mg/L | As necessary | The turbidity of the incoming water should be nil; it is then increased by fertilising algae. | | Iron | < 0.5 mg/L | 1/year | | | Hydrogen Sulphide | < 0.002 mg/L | 1/year | |
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