| Update on grouper aquaculture in the QDPIF Northern Fisheries Center in Cairns, North Queensland Australia (12/2006) |
| Wednesday, 01 November 2006 00:00 |
|
By Antoine Teitelbaum  Where are we at? Applied aquaculture research in Northern Queensland, is at it’s best with the efforts of the Queensland Department of Primary Industries and Fisheries. Researchers at the Northern Fisheries Center, in collaboration with regional partners (ACIAR) have developed protocols for rearing grouper species. Production has been focused on the tiger grouper (Epinephelus fuscoguttatus) and gold spot grouper (Epinephelus coioides). These two species are high on the priority list of ‘new species’ in Australia and their spawning cycle, larval rearing and nursery phases are now well understood with culture techniques developed at NFC currently being adopted by commercial aquaculture operators. ÂBoth of these grouper species are tolerant of fluctuation in salinity, are relatively fast growing and attract high market demand. This makes them perfect candidates for tropical pond aquaculture. In North Queensland, prawn farmers that wish to diversify their production are currently carrying out trials in cages and earthen ponds to test the growth and survival rate of juveniles. On average, these grouper species take 9 to 12 months to reach a commercial size. ÂNFC’s aquaculture system overview At NFC, the grouper broodstock are held in 30 and 60 ton tanks. These recirculation systems are equipped with protein skimmers and biofilters and have both photoperiod and thermal control to allow for the manipulation of the breeding season. All the tanks have an overflow egg collection system. Approximately 10 to 20 fish are held in each tank and most of them spawn naturally without hormone induction. Experience has shown that spawning is influenced by both moon phases and social hierarchy within the tank population. ÂThe larval rearing system is composed of two, 5 m3 figerglass tanks. Water is recirculated through biofilters, protein skimmers, filtration cartridges and UV for sterilization. Metal halide lighting and a heater-chiller device allows full control over the temperature and photoperiod. Both tanks are yellow and are rectangular with rounded corners. They have been tailor made for grouper larviculture. There is a large live prey area at the NFC. Zooplankton (rotifer, Artemias and copepods) is used for rearing grouper larvae. Several species of microalgae are mass cultured, including Proteomonas sulcata, a red coloured cryptophyte algae specially cultivated to feed the copepods. Other species of microalgae are cultured to rear the rotifers and to produce “green†water for the grouper larval rearing stages. Rotifers and Artemia are enriched using commercial enrichment products prior to feeding to larval fish.ÂAfter 40 to 50 days, larvae udergo transformation into juveniles and are transferred to the nursery system. This system is composed of nine 2 ton tanks operated as a flow-through system where water is pre-filtered by sand filtration units. Compressed oxygen is fed into the tanks to keep the DO at an optimum level. The juvenile fish are graded (at least once a week) to prevent cannibalism. Usually, the fingerlings are grown to 10 to 15 grams in the nursery. At this size the rate of cannibalism rapidly declines and the juvenile fish can be transferred to ponds, cages or raceways for experimental or commercial grow-out.  More research and prospects for the regionÂCurrently, experiments are being undertaken to evaluate the ability to transfer day-1 larvae over large distances to be cultured in earthen ponds typical of those found on many aquaculture facilities. If these experiments demonstrate a high survival of larvae after transport and during the pond based larval rearing it could greatly improve the cost effectiveness of rearing grouper species and quickly make it applicable to a lot of areas in the Asia Pacific region. In recent years, aquaculture of barramundi cod (Cromileptes altivelis) has been developed by researchers and industry in South East Asia and is now also being produced commercially in Australia. Coral trout (Plectropomus leopardus) broodstock are a recent addition to the NFC and spawning is forecasted for 2007. Successful rearing of this species will be another breakthrough for the grouper industry in Australia as coral trout fetch very high prices on the live fish trade market in South East Asia and there is a large coral trout fishery of the Great Barrier Reef in Northern Queensland. Another exciting area of research at NFC has recently commenced with the acquisition of giant grouper (Epinephelus lanceolatus) broodstock. This species has great potential as an ideal candidate for aquaculture given its extremely rapid growth rate and tolerance to salinity fluctuation and relatively poor water quality.ÂBeside the ongoing work that is carried out on the early larval stages and nursery culture, a research component on disease management is starting in 2007. Specifically, the use of ozone, to eliminate nodavirus from larvae, which has negatively impacted the grouper aquaculture industry and more generally marine finfish culture in the Asia Pacific region. Some countries in the Pacific region are looking to diversifying their aquaculture industry and grouper farming in ponds or in sea cages could well be a viable option. It sounds very relevant for places like New Caledonia where there are a lot of coastal pond areas and a strong demand for fresh, high value fish. In French Polynesia and in Palau where there is already substantial finfish work being carried out, cultured groupers could match the growing local demand as well the tourism industry’s demand. Not to mention that these products are ciguatera free!  |
