World Aquaculture 31 Fig. 2. Adult Chondracanthus sp. parasitising the gills of the striped trumpeter other new species candidate cultured in Australia is the mulloway, Argyrosomus japonicus, which is parasitized by monogeneans and ciliated protozoans. The research team working on striped trumpeter is aware that when they get their prized juveniles into sea cages the next big challenge will be how to keep them healthy. To date, one myxozoan parasite, Kudoa neurophila (Grossel et al. 2003), has been identified as a problem for the culture of striped trumpeter. This parasite targets the tissues of the central nervous system, which results in behavioral changes and is a possible cause of spinal deformities (Grossel et al. 2003, Grossel et al. 2005). Many infections result in a reduction in flesh quality and, therefore, have the potential to cause major losses to the industry. Good detection methods are available, including a polymerase chain reaction (PCR), which is useful in the detection of the parasite in the early stages of the host’s life cycle (Grossel 2005). K. neurophila appears to only be a problem with larvae and postlarvae, but it remains to be seen if fully scaled juveniles are resistant when kept in high densities. Bacteria are another common problem in most hatchery-reared marine finfish and striped trumpeter are no exception. Both problems have been effectively resolved by treating the hatchery water supply with ozone. This Fig. 3. Gills and operculum of a striped trumpeter parasitised by the Chondracanthus sp. Fig. 4. Adult Caligus sp. parasitising the skin of the striped trumpeter has decreased the bacterial problem and the incidence and severity of infection by the parasite (Smith et al. 2006). Striped Trumpeter and Its Uninvited Guests Very little work has been conducted on the metazoan parasites of wild striped trumpeter outside two surveys off the New Zealand coast (Hewitt and Hine 1972, Hine et al. 2000). During those surveys four species of parasites were collected, including two nematode gut parasites and two monogenean gill parasites. So the discovery of two copepod parasite species on cultured striped trumpeter at the Marine Research Laboratories was of considerable interest. The first copepod (Figure 2) is a previously undescribed Chondracanthus species. No species belonging to the genus has ever previously been recorded from any cultured fish species. The parasite attaches to the hosts gills, operculum and nasal cavities (Figure 3), where their movement and feeding activity irritate the host tissue, which then becomes swollen and inflamed. The second species (Figure 4) belongs to the genus Caligus, which is one of the most common groups causing problems in aquaculture. This group includes Lepeophtheirus salmonis Krøyer 1838 and Caligus elongatus Nordmann 1832, both of which cause major problems in the culture of Atlantic salmon in the northern hemisphere (Costello et al. 2004). The new species occurs on the skin where its movement and feeding activity cause discomfort to the fish host, especially when the parasites are found in high numbers. The host tries to relieve its discomfort by rubbing and this causes the formation of lesions, which are then susceptible to secondary infections. Although the species found on striped trumpeter belong to the genus Caligus, 20 years of farming salmonids in Tasmania suggests it does not parasitize Atlantic salmon. Who are the Guests and How Do They Develop? The discovery of new parasites on striped trumpeter has prompted a variety of descriptive studies. These include detailed descriptions of the male and female for both copepod species. This is a vital step that will aid in future identification if they are ever found parasitizing other fish species. We have also begun to describe their various life stages. Many descriptive studies have been conducted on the developmental stages of various Caligus species (MacKinnon and Piasecki1992, Piasecki and MacKinnon 1995), whereas only one study has been performed on those of the Chondracanthus species (Izawa 1986). During our studies we collect eggs from gravid females, hatch them using water baths and describe each developmental stage as it occurs (Figure 5). This allows us to predict the length of the developmental stages, which will assist us in developing effective treatments and preventing or controlling future outbreaks.
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