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Technical annual report 2000-01



Technical annual report 2000-01


Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295




Made available via the Publications (Legal Deposit) Act 2004 (NT).






Agriculture -- Northern Territory -- Periodicals; Fisheries -- Northern Territory -- Periodicals

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Dept. of Primary Industry and Fisheries

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Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295



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Technical Annual Report 2000/01 295 PROJECT: Reef Fish Aquaculture Project Officers: G. Schipp, J. Bosmans, D. Gore, F. Murakami, C. Kuo and B. Dalliston Location: Darwin Aquaculture Centre, Channel Island Objective: Development of high value finfish, including copepod technology. Justification: To ensure the long-term viability of the Northern Territory finfish aquaculture industry, it is necessary to investigate other candidate species to give farmers the opportunity to diversify production and to meet market demands. The NTG has made a commitment to investigate new, high value, finfish species for aquaculture. 1999/2000 Results: Experiments on the rearing of barramundi cod, Cromileptes altivelis, continued during 2000/ 2001. Investigations focussed on improving water quality and hormone therapy of male fish to assist their reproductive development. Water Quality Improvements were made to the broodstock holding tanks and filtration equipment to overcome problems with poor water quality. Following the relocation of the Aquaculture Centre to Channel Island, the existing filtration system could not cope with the high silt load of the seawater during monsoonal rains and spring tides resulting in turbid water in the fish holding tanks. During periods of poor water quality the barramundi cod had a reduced appetite and appeared lethargic. An upgrade of the sand filter system resulted in a significant improvement in water quality and better health management for the fish. Hormone Therapy Most of our male fish were mature at capture and for the first month in captivity. After two years in captivity they had not re-matured. Also fish that had attained a size of 5.0 kg or more, and were supposed to have undergone sex inversion from female to male, had not shown any signs of maturing. In January 2001, we began a series of hormone treatments for the male fish. Several of the males were implanted with either silastic or cholesterol pellets containing 17 methyltestosterone at 100 g.kg-1. By the end of June 2001, three of the males that had received a cholesterol pellet had matured, as had one of the silastic pellet treated males and two of the control (untreated) males. Maturation was evident by presence of active sperm in a biopsy sample. It is unclear at this stage whether it is the hormone or the improvement in water quality (or a combination of the two) that is having a positive effect.