32 March 2009 How Will We Control Them? Many studies have been conducted on the development of treatment and control methods to reduce the impact that parasites have on aquaculture globally (Raynard et al. 2002, Treasurer 2002, Pietrak and Opitz 2004). Thankfully, neither parasite affecting the striped trumpeter is a major problem when present in low numbers. They only become a nuisance when their numbers increase rapidly (Figure 3). We will monitor parasite numbers to determine if they are affected by water temperature. Even though the project is in its first year we can see that there is a correlation between the chondracanthid parasite numbers and water temperature (Figure 6). In the case of the striped trumpeter, the lack of knowledge of the parasites affecting the species means that there are no treatments in place if the parasite loads increase. This is why it is vital that we use the knowledge gained from studying the developmental stages to identify those most susceptible to treatment. With the planned start of sea cage trials, there is a need for treatments that are easy, cost-efficient and effective as well as being environmentally sustainable and having minimal detrimental effects on the host. During this study we will examine the effects of freshwater, hydrogen peroxide and Neguvon® treatments on Fig. 5. Nauplii larval stage of the Chondracanthus sp. parasitising the striped trumpeter Fig. 6. Average number of chondracanthid parasites per fish compared to the average ambient temperatures both copepod parasites at a number of concentrations and treatment times. We will conduct in vitro trials on the developmental stages for both parasites and determine the effect treatments have on parasite viability. In vitro treatment trials for the adult Caligus sp. will be conducted, with the most effective treatment then being used to treat parasitized fish. Because the method of attachment used by the Chondracanthus sp., in vitro trials aren’t possible, therefore, all treatment trials for the adult parasites will be conducted on parasitized fish. Many of the potential treatments to control parasite infections in aquaculture can be quite harmful to the environment. This is why we hope to develop one that will have minimal impact and could possibly replace other, more harmful, treatment methods. Conclusion Many parasites pose a considerable threat to aquaculture. The discovery of two previously undescribed copepod species on striped trumpeter is a potential challenge to the successful sea cage culture trials. With both parasites now fully described and their developmental stages being properly identified, we can concentrate on the development of control and treatment methods. We hope to eventually demystify general opinions regarding parasites by increasing our knowledge of their biology and effective control methods. Acknowledgments We gratefully acknowledge the excellent technical assistance of Alan Beech, Ross Goldsmid, Anna Overweter, Gavin Shaw and Bill Wilkinson. Experiments were conducted in accordance with University of Tasmania Animal Ethics approval A0008975. The work forms part of a project of the Aquafin CRC, and received funds from the Australian Government’s CRC Program, and the Fisheries Research and Development Corporation and other CRC Participants. Notes 1Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Marine Research Laboratories, Nubeena Crescent, Taroona, Tasmania 7053, Australia 2School of Aquaculture, University of Tasmania, Locked Bag 1370, Launceston. Tasmania 7250, Australia References Battaglene, S. C., D. T. Morehead, J. M. Cobcroft, P. D. Nichols, M. R. Brown and J. Carson. 2006. Combined effects of feeding enriched rotifers and antibiotic addition on performance of striped trumpeter (Latris lineata) larvae. Aquaculture 251:456-471. Bransden, M. P., J. M. Cobcroft, S. C. Battaglene, D. T. Morehead, G. A. Dunstan, M. R. Brown and S. C. Kolkoyski. 2005. Dietary 22:6n-3 alters gut and liver structure and behaviour in larval striped trumpeter (Latris lineata). Aquaculture 248:275-285. Chambers, C. B. and I. Ernst. 2005. Dispersal of the skin fluke Benedenia seriolae (Monogenea: Capsalidae) by tidal currents and implications for sea-cage farming of Seriola spp. Aquaculture 250:60-69. Costello, M. J., L. Burridge, B. Chang and L. Robichaud. 2004. Sea lice 2003 - proceedings of the sixth international conference on sea lice biology and control. Aquaculture Research 35:711-712. Grossel, G. W., I. Dyková, J. Handlinger and B. L. Munday. 2003. Pen- (Continued on page 69)
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