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  • 1
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Development of a formulated pellet to replace ‘bait’ fish in farmed southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), feeds is in progress; however, inherent difficulties have been encountered in conducting large-scale growth trials to evaluate experimental pellet quality. Consequently, alternative methods are being investigated to develop a suitable feed more rapidly. This work explored whether Atlantic salmon, Salmo salar L., could be used as a ‘surrogate’ species for nutrition research on SBT by screening experimental SBT feeds. Atlantic salmon (initial mean weight 161.4 g) were fed a commercial salmon feed (Com.Sal), a commercial northern bluefin tuna feed (Com.NBT), one of three experimental SBT feeds (CRC-A, -B, -C) or dry pelleted pilchards for 42 days, at which time growth was assessed. In vivo and in vitro protein digestibility of the feeds was also evaluated. Weight gain of Atlantic salmon fed Com.Sal (99.8 g) and Com.NBT (93.5 g) were found to be significantly (P 〈 0.01) greater compared to those fed CRC-C (68.2 g) and pilchard (56.1 g). Weight gain of salmon fed the CRC-A (81.6 g) and CRC-B (85.3 g) were also significantly different from the pilchard-fed group, but not from CRC-C. No significant correlation was found between salmon and SBT growth, although difficulties with conducting growth trials on SBT may have limited the ability to compare data. In vitro ingredient digestibilities, however, were used to predict whole feed digestibility, which was found to significantly correlate to weight gain in SBT. Although the use of digestibility techniques appears useful in formulating SBT feeds, the use of a ‘surrogate’ species such as Atlantic salmon to screen SBT feeds needs to be more fully investigated.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 66 (2005), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The haematology of wild southern bluefin tuna Thunnus maccoyii was described using blood samples collected from fish immediately after they were caught. Cytology and cytochemistry revealed that the blood in peripheral circulation is comprised of erythrocytes, reticulocytes, ghost cells, lymphocytes, thrombocytes, eosinophilic granulocytes, neutrophilic granulocytes and monocytes. Reference ranges established were 41·09–55·50% for haematocrit, 0·62–3·00% for leucocrit, 13·25–17·92 g dl−1 for haemoglobin and 2·1–2·9 million erythrocytes μl−1 for erythrocyte count. Differential cell counts showed 94·58 ± 2·15% erythrocytes, 3·99 ± 1·44% leucocytes and 1·43 ± 1·03% thrombocytes (mean ± s.d.). Normal ranges for differential leucocyte counts were 0·00–5·45% for neutrophils, 0·69–12·06% for eosinophils, 0·00–5·03% for monocytes, 46·97–74·32% for lymphocytes and 14·47–43·92% for thrombocytes. Erythrocyte indices, leucocyte types and cytochemistry were comparable to other species of scombrids. Packed cell volume was sensitive to the physiological state of the fish and to sample handling technique.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Atlantic salmon Salmo salar with amoebic gill disease (AGD) were exposed to a graded hypoxia (135–40 mmHg water PO2) and blood samples analysed for respiratory gases and pH at 119, 79·5 and 40 mmHg water PO2. There were no differences in the rate of oxygen uptake between infected and control fish. However, arterial PO2, and pH were significantly lower in the infected fish whereas PCO2 was significantly higher in infected fish compared with controls prior to hypoxia and at 119 mmHg water PO2. At 79·5 and 40 mmHg water PO2 saturation, there were no significant differences in blood PO2 or pH although blood PCO2 was elevated in AGD affected fish at 50% hypoxia (79·5 mmHg water PO2). The elevated levels of PCO2 in fish affected by AGD resulted in a persistent respiratory acidosis even during hypoxic challenge. These data suggest that even though the fish were severely affected by AGD, the presence of AGD while impairing gas transfer under normoxic conditions, did not contribute to respiratory failure during hypoxia.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Amoebic gill disease (AGD) in cultured salmonids causes severe multifocal hyperplastic lesions in the gills with the potential to influence respiratory and acid–base physiology. Atlantic salmon Salmo salar affected with AGD were surgically implanted with dorsal aortic catheters and, following recovery, were confined for 5 min (n = 16) or left undisturbed (n = 8). Confinement caused an acute extracellular acidosis that was corrected in 6 h amongst surviving fish. There was a gradual increase in plasma lactate concentrations that peaked at 1 h post-confinement then declined by 9 h recovery. In a second experiment, AGD-affected fish were confined then recovered either in a tank of static water (n = 9) or while being forced to swim at 1·5 body lengths s−1 (n = 6). There was no significant difference between fish recovered by swimming and those in static water in terms of recovery of the acute extracellular acidosis and lactate accumulations coincident with exhaustive exercise. Confinement severely compromised the survival of AGD-affected Atlantic salmon, although survivors appeared to recover similarly to other studies. Forced swimming of AGD-affected Atlantic salmon following confinement did not facilitate recovery and is unlikely to be a useful strategy for mitigating the effects of stressful episodes such as crowding and fish movement and commercial handling.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A dual enzyme disaggregation method using collagenase and then trypsin was developed that allowed the reproducible initiation of primary cultures from Atlantic salmon Salmo salar gills. Cultures had both epithelial and fibroblast morphology and persisted for an average of 20 passages. Growth was dependent upon a minimum concentration of 5% foetal calf serum (FCS) for fibroblasts and 10% FCS for epithelial cells. Growth was mostly independent of substrate, although epithelial cells showed increased growth on type I collagen gels. Matrigel™ cell culture substrate produced reduced growth of fibroblasts and did not benefit epithelial cell growth. Epithelial cells reacted with monoclonal antibodies (MAbs) against mammalian cytokeratins, and fibroblast cells reacted with MAbs against mammalian fibronectin and type I collagen. The method also produced two long-term cultures: one epithelial and one fibroblast that have been designated RGE-2 and RGF respectively.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 27 (2004), S. 0 
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Previous studies have indicated that when Atlantic salmon, Salmo salar L., are exposed to Neoparamoeba sp. the fish produce anti-Neoparamoeba sp. antibodies. It appears unlikely that these antibodies elicit any specific protection against amoebic gill disease (AGD) as fish with demonstrable activities have been affected by AGD. Experiments were conducted on Atlantic salmon cultured throughout Tasmania to assess the natural production of antibodies towards Neoparamoeba sp. Fish were sampled from areas where AGD was prevalent and from areas where there had been no reported cases. An enzyme-linked immunosorbent assay (ELISA) was used to measure anti-Neoparamoeba sp. antibody activities in serum. All fish from sea water had antibody activities greater than the negative control fish, including fish from areas with no reported cases of AGD. Time trial samples indicated that time after transfer to sea water did not appear to be a significant (P 〉 0.05) factor in antibody activity, however location was (P 〈 0.05). There was no agreement (corrected κ value, 0.16) between the ELISA result and the isolation of Neoparamoeba sp. from the gills of the same fish. The results suggest that Atlantic salmon in seawater culture in Tasmania produce anti-Neoparamoeba sp. antibodies regardless of infection history, suggesting the presence of Neoparamoeba sp. in the environment.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 26 (2003), S. 0 
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Amoebic gill disease is the main disease affecting the salmonid industry in Tasmania, but no information on the distribution of the causative pathogen, Neoparamoeba pemaquidensis, in the aquatic environment is available. This pilot study aimed to determine temporal and spatial distributions of paramoebae species in the water column, using an immuno-dot blot technique. Water samples were collected from inside fish cages at various depths (0.5, 5.5 and 11.0 m) in both summer and winter, as well as various distances (0, 0.5, 240, 280, 750 and 1100 m) away from the sea cage and farming site. Paramoebae densities were estimated using the most probable number technique (MPN). Temperature, salinity, dissolved oxygen, turbidity, nitrite and nitrates, and bacterial counts were measured for each water sample. Data were analysed using a residual maximum likelihood test and significant associations between paramoebae densities and environmental factors were analysed. Results showed that densities were significantly higher in summer (P = 0.017), at 5.5 m depth (P = 0.029), and reduced to the lowest density at 1100 m away from the cage sites (P = 0.008). Bacterial counts, turbidity and temperature were found to be significantly associated with paramoebae densities.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Journal of fish diseases 20 (1997), S. 0 
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In autumn 1993, an outbreak of gill disease occurred in Atlantic salmon, Salmo salar L., smolts farmed in the Huon estuary in southern Tasmania, Australia. Histologically, the presumptive primary lesion appeared as focal, sometimes full thickness, gill necrosis, which showed no host reaction in the initial stages. Healing of these damaged areas gave rise to conspicuous expanded tips or clubbing of gill filaments. The term clubbing and necrosis gill (CNG) syndrome is suggested to include both these histological features. Fusion of lamellae proximally along the filament, often with vascular dilation, was also a feature of the condition. Similar lesions have been described previously in the literature, but the initial necrosis followed by the very prominent clubbing of filaments was sufficiently different from previous descriptions to warrant designation of this condition as a distinct entity.
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  • 9
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Previous studies have demonstrated that β-glucans stimulate Atlantic salmon, Salmo salar L., head kidney macrophages both in vitro and in vivo and increase protection against various pathogens. Based on our previous work that showed potent immunostimulatory CpG motif-containing oligodeoxynucleotides increased resistance to amoebic gill disease (AGD), the present study investigated the immunostimulatory effects of three commercial β-glucan-containing feeds and their ability to increase resistance to AGD. All three commercial β-glucans were able to stimulate the respiratory burst activity of Atlantic salmon head kidney macrophages in vitro, albeit at different times and concentrations. However, dietary incorporation of the β-glucans was unable to stimulate the in vivo respiratory burst activity of head kidney macrophages, or serum lysozyme production, and did not increase resistance against AGD. However, this trial showed for the first time that a small subpopulation of Atlantic salmon subjected to a severe AGD infection was able to resist becoming heavily infected and furthermore survive the challenge.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 28 (2005), S. 0 
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Aquaculture in Tasmania is mostly carried out in estuaries. These estuarine habitats show a great variety and form unique environments in which Neoparamoeba pemaquidensis, the amoebic gill disease (AGD)-causing protozoan, may or may not survive. Tasmania is divided into two zones, one where AGD is present and one where AGD is absent, but any ecological data to rationalize this distribution is lacking. In in vitro trials N. pemaquidensis strains were exposed to different concentrations of ammonium sulphate, copper sulphate, copper sulphate and tannin, and different Neoparamoeba densities, salinities and temperatures. A trial using field water samples investigated the survival of N. pemaquidensis in waters sourced from AGD-free and AGD-positive zones, and water analysis was performed to determine any differences. Significantly decreased protozoan survival was found with exposure to increasing copper sulphate concentrations from 10 to 100 000μm (P 〈 0.001), salinity of 15‰ (P 〈 0.001), low Neoparamoeba densities of 625 and 1250 cells mL−1 (P = 0.0005), and water sourced from Macquarie Harbour (P 〈 0.001). The water chemistry of this AGD-free zone showed significantly lower dissolved calcium and magnesium concentrations which may contribute to this area being AGD-free. Understanding of the ecology of N. pemaquidensis will enable better control and prevention strategies for Tasmanian salmon growers.
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