Jade perch
Scortum barcoo
Revised by Ross Lobegeiger, Bribie Island Aquaculture Research Centre
The Barcoo grunter, Scortum barcoo, is a freshwater finfish native to the Lake Eyre and Bulloo-Bancannia catchments. The natural habitat of the barcoo grunter includes the low gradient rivers and creeks of the Lake Eyre Catchment. Waters are generally highly turbid and have a wide temperature and conductivity range.
Barcoo grunter is marketed under the name Jade perch.
It should be noted that currently, very little independent
research on the aquaculture of Jade perch has taken place. The species is
readily produced by hatcheries and has shown early success in pond growout and
intensive tank culture. There is a narrow range where optimum growth rates occur
which is probably 22oC to 28oC. Growth is negligible below 20oC. Marketable fish
of 350 to 800gms can be grown in 8 to15 months in earth ponds.
Culture environment
Limited commercial experience suggests that Jade perch
appear to be well suited to production in well-managed recirculation tank
systems with the aid of effective biological filtration. Limited commercial
production has also occurred in purpose built earth ponds. Pond sizes can vary
from 0.2 to 0.5 hectare surface area with depths of 0.7 to 2.5 metres. It is an
advantage to have all ponds easily drainable.
Breeding and fry production
In their natural habitat, Jade perch spawn during the
summer floods when water temperatures are above 23oC. In captivity the sexually
mature broodstock are induced to spawn with a hormone injection. The
first-feeding larvae are approximately 5 mm 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 to 4 weeks (15 mm long). Fingerlings can
grow to 30 mm to 50mm in 8 to 12 weeks. These fingerlings can then be stocked
into grow-out ponds or into 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. 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 is dependent 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 passed through a filter screen to exclude predators. In recirculation systems, Jade perch have been reported to reach 450 g after 4 months and 800 g in 7 months from an advanced fingerling size. Maximum densities are usually about 40-50 kg per cubic metre.
Careful management of stocking densities and feed rates will prevent excessive NH3 concentrations. Jade perch are able to tolerate a pH of between 6 and 9, with the desired range between 6.5 and 8.5. Salinity levels of 5 grams per litre sodium chloride are acceptable for long term exposure and can be used to treat ectoparasite and fungal diseases.
Dissolved oxygen (DO) levels of 4 mg per litre or greater encourage maximum growth and survival. Aeration (paddlewheels and/or aspirators) is essential for commercial production. Aeration and water exchanges need to be increased when pond water temperatures exceed 30oC. Many farmers cease feeding when temperatures fall below 16o. Growth rates decline rapidly when water temperatures fall below 20oC. Handling fish below 17oC may cause mortalities. Large-scale mortalities have occurred at temperatures in ponds below 13oC.
Jade perch are omnivores consuming zooplankton, small crustaceans, aquatic insects, molluscs, algae and plant material. Although no specific research has been conducted on the 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 with the use of 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 to 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 to 1000 gram size, however, no detailed market studies have been done.
Conclusions
Successful Jade perch farming is a function of stocking rate, water quality, diet and stock management. In well-managed ponds industry suggests that production of 5 to 10 tonnes per hectare is attainable. A number of silver perch growers have produced this species and found them to be very hardy and are positive about the potential. Currently production has been targeted at the live fish market and sold in the three east-coast capital cities. Initial market reaction has been positive to the attractive colour and high weight to length ratio of the species.
References
Long, P. and Humphery, V. (1995). Fisheries Study Lake Eyre Catchment. Information Series, QI97080. Queensland Department of Primary Industries and Fisheries.
Merrick, J.R. and Schmida, G.E. (1984). Australian Freshwater Fishes . Griffin Press Ltd. Adelaide.
Rowland, S., J., Landos, M., Callinan, R., B., Allan, G., L., Read, P., Mifsud., C., Nixon, M., Boyd, P. and Tully, P. (2007). Development of a Health management Strategy for the Silver Perch Aquaculture Industry, NSW Department of Primary Industries - Fisheries Final Report Series No. 93, ISSN 1449-9967
Additional fisheries information
Perch Profit, (2002), Economic and information package for farming perch in Australia. Available through Queensland Government Publications.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
File No: F0149
Last updated 6 December 2007
