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Growing and harvesting jade perch

Breeding and fry production

In their natural habitat, jade perch spawn during the summer floods when water temperatures are above 23°C. In captivity the sexually mature broodstock are induced to spawn with a hormone injection. (Note: many chemicals used in aquaculture, such as hormones, require veterinary advice and prescriptions before use. Always check before use.)

The first-feeding larvae are about 5mm long and can be reared in a pond environment managed to achieve a stable zooplankton bloom (rotifers and copepods). Survival rates of 30% or higher are possible with larvae metamorphosing into fingerlings in 3-4 weeks (15mm long). Fingerlings can grow to 30-50mm in 8-12 weeks. These fingerlings can then be stocked into growout ponds or recirculation systems.

Growout

Growth rates vary depending on water temperature and management strategies. To achieve superior growth rates fingerlings should be regularly graded into size classes, either in tanks or in earth ponds, until they reach 150mm. This prevents excessive size variation at harvest and inefficient feeding rates.

Stocking density

The current industry experience suggests that stocking rates in ponds should be up to a maximum of 15,000 fish per hectare, although no systematic research has been undertaken on husbandry practices. In tanks, the stocking density depends on the capacity of the system but appears to be at least comparable with those used for barramundi.

Prior to stocking, ponds are drained, well dried and, if necessary, limed and cultivated. They are then filled with water that has been passed through a filter screen to exclude predators. In recirculation systems, jade perch have been reported to reach 450g in 4 months and 800g in 7 months from an advanced fingerling size. Maximum densities are usually about 40-50kg per cubic metre.

Careful management of stocking densities and feed rates will prevent excessive ammonia concentrations.

Feed

Jade perch are omnivores. They eat zooplankton, small crustaceans, aquatic insects, molluscs, algae and plant material. Although no specific research has been conducted on their dietary requirements, commercially available artificial diets are readily accepted at both fingerling and adult stage.

Pellet size varies with the size of the animal. The food conversion ratios (FCR) vary depending upon the level of management with 1.2:1 for fingerlings to 1.6:1 for growout being achievable. Care should be taken when feeding, as jade perch are voracious feeders and overfeeding can occur. Netting or the placement of nylon scarewire across ponds will assist in the control of bird predation.

Harvesting

Ponds are primarily harvested using seine nets, either partially or for a complete harvest.

It is critical to harvest fish in good condition to ensure fish are not stressed during purging and transport to market. Purging the fish in clean water for 7-14 days depending on temperatures normally removes any off flavours. The addition of salt is recommended for purging.

Live fish marketing suggests that fish should be sold in the 650-1000g size; however, no detailed market studies have been completed.

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