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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 27 (1996), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Anadromous Arctic charr, Salvelinus alpinus (L.), from the River Halselva in Finnmark, northern Norway, were used as broodstock for the production of smolts. During the smolting period the fish were either shielded from normal working routines, subjected to normal work routines, or exposed to excessive work routines (stress) within the hatchery. None of the handling routines affected the gill-Na-K-ATPase activity, or the hypoosmoregulatory capacity of the charr. Compared with normal handling, neither stress nor shielding caused any significant difference in the migratory behaviour of the charr, in the duration of the sea residence, or in homing success. However, the stressed group did show a lymphocytopenia at end of the rearing period.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Aquaculture research 32 (2001), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was significantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per fish respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected fish. Such behaviour has previously been interpreted as a response by the fish to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected fish, and 47% of the fish caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all fish from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance. High salmon lice infections may therefore have profound negative effects upon wild populations of sea trout. At the unexposed location, the infection intensities were low, and few fish carried more than 10 lice. These are probably within the normal range of natural infection and such intensities are not expected to affect the stock negatively.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Endurance of farmed and sea-ranched Atlantic salmon Salmo salar L. males was analysed during spawning time. The fish were endurance tested at different swimming speeds (1.6–2.1 m s−1) in forced swim trials. The sea-ranched males (51-65 cm, n= 20) fatigued significantly earlier than the farmed males(59-72 cm, n= 20),although the sea-ranched males were significantly smaller than the farmed males. When the size difference between the two groups were corrected for, no significant difference in the endurance of the two groups was found. Farmed salmon had a significant higher fat content in white muscle (4.7%) than sea-ranched salmon (1.1%).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 26 (1995), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The survival of salmon lice. Lepeophtheirus salmonis (Krøyer) on Arctic charr. Salvelinus alpinus (L.). in fresh water was studied. The results showed that salmon lice were able to survive for up to 3 weeks, in contrast with previous published information that the parasite is quickly shed when the fish enters fresh water.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 25 (1994), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Hatchery-reared 1-year-old Atlantic salmon post-smolts (Salmo salar L.), artificially infected with salmon lice [Lepeophtheirus salmonis (Krøyer)] copepodids, were found to suffer from primary alterations (increased cortisol levels) at early lice stages. Secondary alterations, such as osmotic stress (increased chloride levels), first occurred after the preadult stages of the lice appeared. Fish with the highest salmon lice infections died throughout the experiment. Seven years of field investigation of Trondheimsfjorden showed that Atlantic salmon post-smolts descending coastal waters can become heavily infected with salmon lice. The migrating post-smolts were only infected with the chalimus stages, showing that the fish had only recently left the rivers. The infection level, however, varied considerably between the years, and, in 1998, the infection was higher than previous years. The experimental results have been combined with the field data to appraise the consequences of the infection.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 32 (2001), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of metomidate anaesthesia on levels of plasma cortisol, glucose, haematocrit and chloride in Atlantic salmon (1+) (Salmo salar L.), after a 2-h transport and during a 48-h recovery period were investigated. The use of metomidate anaesthesia during transport led to a reduced release of cortisol and significantly lower levels of plasma cortisol after a 48-h recovery period. Plasma glucose did not return to basal level after a 48-h recovery period, indicating that even longer recovery may be needed for the fish to return to a pre-stress state. The results show that metomidate anaesthesia combined with a recovery period lessens the stress burden imposed by hauling and transport.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 43 (1993), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two groups of anadromous Arctic charr (Salvelinus alpinus) (size 200–350 mm) reared in heated water (6–12° C) under simulated natural photoperiod were individually tagged and released in spring 1988. The fish were released at two sites, in the estuary of the River Halselva and in the fjord, 2 km from the river mouth. Growth, timing of migration and survival of these hatchery-reared fish was compared to that of wild anadromous charr of the same size over a 4-year period. The hatchery-reared charr had poorer growth than the wild fish during their first year in sea water. They also resided longer in the sea and had a slightly lower survival than wild fish. During the second year, hatchery-reared charr displayed good growth, and after the third sea-season the fish were ready for slaughter at a size of approximately 800g. The results suggest that the successful development of Arctic charr ranching will be dependent upon production and release strategies that lead to improved migratory and feeding behaviour of the fish during their first season at sea.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Stomach content analyses were conducted on Atlantic salmon Salmo salar post-smolt (average size, 119–154 mm fork length, LF) caught in eight large Norwegian fjord systems along a north–south geographical axis during 1998–2001. In general, post-smolts from southern Norway showed low feeding intensity in the fjords, whereas extensive feeding was observed in fjords in the northern and middle parts of Norway. The marine diet mainly included different crustaceans and in particular marine pelagic fish larvae (sand-eels Ammodytes spp., herring Clupea harengus and gadoids), but with a substantial spatial and annual variation in prey diversity and feeding intensity. Insects were most frequently taken in the estuary, although fishes often made a large contribution in mass. In contrast, fishes, and to some extent various crustaceans (particularly Hyperiidae, Gammaridae, Euphausiacea and Copepoda) dominated the diet in the middle and outer parts of the fjords, where post-smolts also fed more extensively than in the inner part. The results indicate that extensive feeding immediately after sea entrance may be more common for post-smolts in the northern and middle parts of Norway, than in the southern fjords. The observed differences in post-smolt feeding may be due to spatial and temporal differences in prey availability within and between the different types of fjord systems, and this might influence post-smolt growth and survival.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 58 (2001), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Exposure of sexually mature pre-spawning Atlantic salmon Salmo salar to Fossbekk water (pH 5·2) for 7 days led to a significant reduction in critical swimming speed (U-crit) in females but not in males. Exposure to Fossbekk water +A1 (as AlCl3) for 24 h led to a significant reduction in U-crit in both males and females. In contrast to fish exposed for 7 days to Fossbekk water, fish exposed to Fossbekk+A1 had accumulated much more aluminium and mucus on their gills. Losses of plasma ions were similar in both groups exposed to acid water. Blood glucose was twice as high in fish exposed to Fossbekk water for 7 days compared with fish exposed to Fossbekk+A1 for 24 h. Plasma cortisol was still elevated compared with controls after exposure to Fossbekk water for 7 days. Possible mechanisms for the observed decrease in U-crit at the different exposures are discussed.
    Type of Medium: Electronic Resource
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