By Tony Bart
We (Challenger Institute of Technology) have been culturing Silver Perch ( Bidyanus bidyanus ) at our Fremantle campus for several years now as part of the Certificate and Diploma of Aquaculture training. Although Challenger’s marine hatchery is operated by its research arm, the Australian Centre for Applied Aquaculture Research (ACAAR) and has Yellowtail Kingfish (Seriola laladi), Barramundi ( Lates calcarifer ), Mulloway (Argyrosomus japonicas ), Pink Snapper ( Pagrus auratus) and Black Bream (Acanthopagrus butcheri ) broodstock access is also available to freshwater Silver Perch brood stock through a farmer at Toodyay.[private]
The broodstock are injected with HCG at a rate of 200 IU per kilogram for females and 100 IU per Kilogram for males. Once the broodstock spawn and the eggs hatch the larvae are brought down to Fremantle where the larvae are taken through the larval period which takes approximately 28 days. The larvae are cultured in 5000 litre tanks maintained by a recirculating system and they are fed initially Artemia nauplii from days 4 to 6 and then enriched metanauplii for approximately 2 weeks. After this period the larvae are weaned onto a variety of artificial larval feeds ranging from 250 to 500 microns.
Fingerling and juvenile Silver Perch are then raised by the students at the Fremantle campus in 5000 Litre tanks and this year some of the juveniles were used to stock the 5000 litre aquaponics tank at the Murdoch horticulture campus.
ACAAR undertook a commercial run for a local WA company in 2009 when we secured eggs from the broodstock and cultured the larvae in an intensive RAS system associated with several 5,000 Litre culture tanks. We ran the RAS with freshwater, fed Artemia as the live feed source, weaned them onto native fish crumble and ended up delivering just over 200,000 fully weaned juveniles to the company in mid-December 2009.
The culturing of Silver Perch larvae entirely in tanks is unusual in that farmers would normally release five day old larvae into large ponds that have been prepared so that there is a large zooplankton population for the larvae to feed on. The advantage of culturing larvae and fingerlings in recirculation tanks is that the fish are safe from pond predators such as birds, tortoises etc and it is a lot easier to harvest the fish from a tank than a large pond. The down side is that a considerable amount of work must be done to operate and maintain an recirculating aquaculture system. As Challenger’s hatchery is in the centre of a busy seaport such as Fremantle the option for pond culture was very limited.
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