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  • 1
    Electronic Resource
    Electronic Resource
    Crowding causes prolonged leucopenia in salmonid fish, despite interrenal acclimation (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 30 (1987), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Crowding for 3 weeks significantly reduced the coefficient of condition of both brown trout and rainbow trout. However, acclimation of the hypothalamic-pituitary-interrenal (HPI) axis, as assessed by changes in plasma cortisol levels, occurred within 6 days for brown trout and within 10 days for rainbow trout. Blood lactate levels were significantly reduced in the crowded fish of both species throughout the experiment. Sexual maturation of the male fish significantly elevated the number of circulating red blood cells in both species, reduced the lactate levels in brown trout and elevated cortisol levels in the rainbow trout. Despite the relatively rapid interrenal acclimation, the numbers of thrombocytes and lymphocytes in the blood of both species were significantly reduced during the period of crowding and it is concluded that changes in the composition of circulating blood cells are more reliable indicators of chronic crowding stress than are plasma cortisol levels. These findings are discussed in relation to the role of the HPI axis in suppressing the defence systems of salmonid fish during periods of chronic stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1987.tb05799.x
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  • 2
    Electronic Resource
    Electronic Resource
    Ectoparasite induced changes in epidermal mucification of the brown trout, Salmo trutta L. (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 25 (1984), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The apparent effects of environmental factors on skin structure in hatchery-reared brown trout are shown to be mediated by the influence of these factors on the skin parasite population. The presence of ectoparasites promotes a reduction in the concentration of epidermal mucus-secreting goblet cells, the magnitude of which is related to the intensity of infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1984.tb04857.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sexual differences in the incidence and severity of ectoparasitic infestation of the brown trout, Salmo trutta L. (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 16 (1980), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hatchery-reared and wild brown trout, Salmo trutta L., were examined for skin ectoparasites during their spawning period in 1977 and 1978. A total of eight genera of parasites, comprising five ciliates, one flagellate, one monogenean and one parasitic fungus, were identified with as many as five different genera occurring on a single fish. Sexually mature male fish were more frequently or more severely infested by species of Ichthyophthirius, Scyphidia, Gyrodactylus and Saprolegnia than were immature fish of either sex or mature female fish. The differences in ectoparasitic loading could not be correlated with known, seasonal changes in the mucus-producing potential of the epidermis. These findings are discussed in relation to the defence mechanisms of teleost fish and to some of the endocrinological changes that occur in salmonid fish during the spawning season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1980.tb03746.x
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  • 4
    Electronic Resource
    Electronic Resource
    Environmental stress and the survival of brown trout, Salmo trutta (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 21 (1989), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The hypothalamic-pituitary-interrenal axis of the brown trout, Salmo trutta, is activated in response to most forms of environmental stress. This results in an elevation of blood cortisol levels.2. Experimental elevation of blood cortisol levels in otherwise unstressed brown trout caused a dose-dependent increase in mortality rate due to disease. In our studies., Saprolegnia-infection, furunculosis and bacterial fin-rot were the principal diseases.3. Chronic cortisol elevation also suppressed several of the endocrine processes controlling sexual maturation, resulting in a significant reduction in the size of the gonad in both male and female fish.4. It is argued that many of the deleterious effects of sublethal pollution (including acidification) on natural trout populations can be attributed to chronically-elevated blood cortisol levels and that a knowledge of such physiological changes would allow an assessment of the impact of pollution events and act as an early warning of potential disease and recruitment problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1989.tb01347.x
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  • 5
    Electronic Resource
    Electronic Resource
    Further studies of an epizootic of perch Perca fluviatilis L., of uncertain aetiology (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish diseases 2 (1979), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. The geographical distribution of an epizootic of perch Perca fluviatilis L., characterized by severe epidermal lesions and marked fish kills, is described. A wide variety of fungal and bacterial infections were found in diseased fish but the evidence suggests that they were not the primary cause of this condition. The primary pathogenic agent (assuming that it exists) or predisposing environmental factor has yet to be discovered. The severity of this disease is illustrated by monitoring the course of the epizootic in the perch population in Windermere. All age groups of fish were affected during the course of one year although the fish at spawning time appeared to be particularly vulnerable. There was a dramatic increase in the perch mortality in Windermere in 1976 and it is estimated that over 98% of the adult population (over 1 million fish) died in that year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2761.1979.tb00172.x
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in serum parameters of Saprolegnia-infected brown trout, Salmo trutta L. (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish diseases 2 (1979), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. Fungal infection of both wild and hatchery-reared sexually mature brown trout, Salmo trutta L., was caused by Saprolegnia diclina Humphrey Type 1. The major ions in the serum of infected fish were all significantly reduced in concentration and it is suggested that the primary cause of death was osmoregulatory breakdown resulting in a lethal haemodilution. Severe hypoproteinaemia and a significant reduction in the albumin/globulin ratio were reflected in the electro-phoretogram of the serum proteins from infected fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2761.1979.tb00159.x
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  • 7
    Electronic Resource
    Electronic Resource
    Frequency and distribution patterns of Saprolegnia infection in wild and hatchery-reared brown trout Salmo trutta L. and char Salvelinus alpinus (L.) (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish diseases 1 (1978), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. Fungal infection of sexually mature brown trout and char was associated with a particular type of Saprolegnia exhibiting a low degree of homothallic sexuality. Hatchery-reared brown trout were more severely infected (in terms of the % area of the body covered with the fungus) than were wild fish. The fins of hatchery-reared fish were particularly prone to Saprolegnia infection regardless of sex. In wild brown trout, a sexual difference in the pattern of infection was demonstrated. The flanks of the male fish appeared to be more prone to infection when compared with the female and there was a greater susceptibility of the caudal and ventral fin of the female when compared with the male. Evidence is presented which suggests that the incidence of infection in mature male salmonid fish prior to spawning is significantly greater than in the females. This difference may not be apparent in spent fish after spawning. These findings are discussed in relation to the background concentration of fungal spores in the water, the behavioural characteristics of spawning fish and differences in epidermal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2761.1978.tb00006.x
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  • 8
    Electronic Resource
    Electronic Resource
    Differences in the sensitivity of brown trout, Salmo trutta L., and rainbow trout, Salmo gairdneri Richardson, to physiological doses of cortisol (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 34 (1989), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Interspecific differences in the stress response of fish may be due, in part, to differences in the sensitivity of target tissues to cortisol. The relative response of brown and rainbow trout to a standardized dose of cortisol was assessed by monitoring condition (K factor), the number of circulating lymphocytes and mortality due to disease, following cortisol treatment. Cortisol implantation resulted in a significant decline in K factor and number of circulating lymphocytes in immature brown trout, but not in immature rainbow trout, despite plasma cortisol levels being similar in both cases. Cortisol implantation in mature brown and rainbow trout significantly increased the mortality rate due to bacterial and fungal infection compared with control fish. Furthermore, the mortality rate due to disease was significantly greater in brown trout than rainbow trout, despite both groups receiving similar doses of steroid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1989.tb03355.x
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  • 9
    Electronic Resource
    Electronic Resource
    Poor water quality suppresses the cortisol response of salmonid fish to handling and confinement (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 30 (1987), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Confinement of brown trout in small troughs of static water for 1 h at a density of six fish 251−1 stimulated the hypothalamic-pituitary-interrenal axis and resulted in an elevation of plasma cortisol from basal levels (less than 2 ng m1−1) to about 100 ng m1−1, the degree of stimulation being dependent upon water temperature. Confinement at a density of 30 fish 251−1 resulted in a 50% suppression of this response. It is demonstrated that this effect is mediated by changes in water chemistry and not by crowding per se. Experimental manipulation of the water chemistry showed that reduced pH (7.1 → 6.3), elevated free CO2 (63 → 520 μmoll−1) or elevated ammonia (8 → 1300 μg 1−1 as total ammonia nitrogen) had no individual effects on the interrenal response to acute confinement. Elevated ammonia in combination with reduced pH significantly increased the plasma cortisol levels in response to acute confinement, whereas a combination of reduced oxygen (100 → 20% saturation), elevated free CO2 and elevated ammonia markedly suppressed (∼ 50%) the cortisol response of both brown trout and rainbow trout to acute confinement in a manner similar to that observed with trout at high densities. A compensatory increase in plasma cortisol levels was observed during the subsequent recovery of fish which had been confined for 1 h in water of poor quality. These findings are discussed in relation to the exposure of fish to multiple stresses and to the role of corticosteroids in the stress response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1987.tb05761.x
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  • 10
    Electronic Resource
    Electronic Resource
    Changes in blood cell composition of the brown trout, Salmo trutta L., during the spawning season (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 29 (1986), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Differential blood cell counts were monitored in three different strains of brown trout through three separate spawning seasons. A consistent elevation in the number of circulating erythrocytes was observed in sexually mature male fish (compared with immature fish of either sex) during October-December of each season. A marked lymphocytopenia also occurred during October in mature fish of both sexes with lymphocyte numbers still being significantly depressed as late as March the following year. It is concluded that the use of haematology as a technique for assessing the state of health of salmonid fish must take into account the sex and state of maturation of the fish. The possible consequences of changes in haematology during sexual maturation are discussed in terms of respiratory function and defence against pathogenic challenge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1986.tb04950.x
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