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  • 1
    Electronic Resource
    Electronic Resource
    Primary and secondary indices of stress in the progeny of rainbow trout (Oncorhynchus mykiss) selected for high and low responsiveness to stress (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 44 (1994), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A series of pooled gamete matings was carried out employing eggs and milt from mature male and female rainbow trout selected for a consistently high- or low-responsiveness to stress, as indicated by post-stress plasma cortisol elevation. Development of the progeny was closely monitored and the responsiveness to stress of the progeny of high-responding parents and the progeny of low-responding parents was assessed by two methods. For a period of 14 months, at approximately monthly intervals, the plasma cortisol elevation evoked by a standardized confinement stress was determined in fish from each group, and secondly, on one occasion, the time-course of the plasma cortisol response to a 24-h period of confinement was monitored. Progeny of high-responding parents snowed a significantly greater cortisol response to stress than the progeny of low-responding parents during both testing procedures. However, when the effect of a 14-day confinement stress was examined, high-responding progeny showed a more rapid recovery of plasma cortisol levels, while levels in the low-responding progeny, although initially lower, showed a more sustained elevation. To assess the possible functional implications of these observations, circulating lymphocyte numbers, an immunologically important cortisol-sensitive component of the blood cell complement, were determined. The duration of the lymphocytopenia observed following the onset of confinement was found to be related to the initial, not the sustained, cortisol response. These data suggest that manipulation of the sensitivity to stress of fish is feasible by selective breeding, but that careful.choice of the indices employed to identify traits considered desirable is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1994.tb01591.x
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in plasma cortisol and cortisone dynamics during stress in two strains of rainbow trout (Oncorhynchus mykiss) (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 43 (1993), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plasma levels of cortisone, a steroid hormone of potential physiological significance in fish, have rarely been measured. This study examines the interrelationship between circulating levels of cortisone and the major teleost corticosteroid, cortisol, in the blood of two strains of rainbow trout subject to confinement stress, a condition know to stimulate corticosteroidogenic activity. In unstressed fish from both strains, mean plasma cortisol levels were within the range 0.4–7.5 ng ml−1. Mean plasma cortisone levels were within the range 7.1–15.9 ng ml−1. Plasma cortisol levels were elevated within 5 min of the onset of strees and reached peak values within 45 min, although there was a marked difference betweed the maxima observed in the two strains (strain 1:70 ng ml−1; strain 2:150 ng ml−1). The rate of increase of plasma cortisone levels during strees was more rapid than that of cortisol, maximum values (strain 1:100ng ml−1; strain 2:160 ng ml−1) being reached within 10 to 20 min of the onset of stress. This rapid stress-induced elevation of plasme cortisone has not previously been reported in fish. We suggest that rapid conversion of cortisol to cortisone during the initial response to stress accounts for the appearance of large amounts of cortisone in the blood, indicating that circulating for the appearance of large amounts of cortisone in the blood, indicating that circulating levels of cortisol alone do not fully reflect the secretory activity of the interregnal during the initial of cortisol alone do not fully the secretory activity of the interregnal during the initial phase of the stress response. The results also indicate that the rate of clearance of cortisone from the circulation may be a major factor in determining stress-stimulated levels of plasma cortisol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1993.tb00415.x
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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of biochemical methods for the non-destructive identification of sex in upstream migrating salmon and sea trout (2005)
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    Journal of fish biology 67 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Female-specific markers of reproductive activity [plasma 17β-oestradiol (E2), vitellogenin (VTG) and alkali-labile phosphoprotein phosphorous (ALP)] were measured over 12 months in a captive population of brown trout Salmo trutta. During the early months of the reproductive season (February to May) and using the concentration of plasma E2 or plasma ALP as a marker for females the proportion of fish in which sex was misidentified was high (15–50%). The misidentification rate was considerably lower (1–8%) using plasma VTG. Preliminary evaluation of a commercial immunochromatographic VTG test system as a screen for the presence or absence of VTG in plasma from brown trout provided results that were consistent with those obtained from direct measurement of plasma VTG levels by enzyme-linked immunosorbent assay (ELISA). These preliminary conclusions were verified by sampling upstream-migrating anadromous brown trout, sea trout, and Atlantic salmon Salmo salar trapped over a 6 month period. Plasma E2 levels did not satisfactorily discriminate between male and female sea trout and Atlantic salmon. Plasma VTG levels in both species, however, were bimodally distributed and it was assumed that this divergence corresponded to male (plasma VTG levels 〈10 μg ml−1) and female (plasma VTG levels 〉800 μg ml−1) fishes. Plasma ALP provided a more accurate indication of sex in the wild Atlantic salmon and sea trout than was suggested by the pilot study on captive brown trout. The commercial immunochromatographic VTG test system provided results that were wholly consistent with the data obtained from the trapped fishes by direct measurement of plasma VTG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2005.00853.x
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  • 6
    Electronic Resource
    Electronic Resource
    Contrasting seasonal modulation of the stress response in male and female rainbow trout (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Between June and September the magnitude of the plasma cortisol response of maturing male and female rainbow trout to confinement was indistinguishable. A progressive increase in confinement-induced cortisol levels in both sexes occurred during May to September, associated with the seasonal rise in water temperature. Between September and January a reduction of 〉50% in the magnitude of the cortisol response to confinement in male fish (but no decline in females) coincided with declining water temperature and significant increases in plasma 11-ketotestosterone and elevated plasma testosterone levels. Plasma oestradiol-17β levels were significantly greater in females than males throughout the study period and this difference was maximal between September and January. However, plasma testosterone was also elevated in females during this period and levels overall were higher than those in male fish. Previous studies have shown oestradiol-17β and testosterone to have diametrically opposed effects on stress responsiveness in trout, with the former enhancing, and the latter suppressing, the cortisol response to a stressor. The relative roles of androgens, estrogen and water temperature in modulating the stress responsiveness of rainbow trout are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00764.x
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  • 7
    Electronic Resource
    Electronic Resource
    Indicators of reproductive performance in rainbow trout Oncorhynchus mykiss (Walbaum) selected for high and low responsiveness to stress (2000)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 31 (2000), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A number of indicators of reproductive performance were assessed in rainbow trout divergently selected on the basis of their plasma cortisol response to a standardized stressor. For both male and female rainbow trout Oncorhynchus mykiss (Walbaum), body weight was significantly related to stress responsiveness. High-responding (HR) females were significantly heavier than low-responding (LR) females overall, and HR males were significantly heavier than LR males overall. There was no significant difference in the specific growth rate (SGR) of HR and LR female fish during the experimental period, whereas in contrast the mean SGR of HR males was significantly greater than that of LR males. The divergent confinement-induced levels of blood cortisol in HR and LR groups were stable for more than 1 year after selection. There was no significant difference in the extent to which confinement stress reduced blood oestradiol-17β levels in HR and LR females, despite a large difference in relative blood cortisol levels. The onset and rate of ovulation was similar within the HR and LR groups. Differences in fecundity, relative fecundity and egg volume and weight were wholly attributable to the different mean body weights of the HR and LR fish. There was no difference between the sperm counts of HR and LR males. There was significantly higher mortality among eggs derived from HR parents overall between fertilization and hatch, but maximum mean mortality did not exceed 12%. Mean time to eyeing in the HR groups was 224 degree days, and in the LR groups was 244 degree days. Hatching commenced at 344 and 347 degree days in the HR and LR groups, respectively, and was complete within 412 and 416 degree days respectively. Overall, selection for stress responsiveness was associated with no significant benefits or costs in reproductive performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.2000.00450.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 skin structure associated with elevated androgen levels in maturing male brown trout, Salmo trutta L. (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 26 (1985), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Increases in epidermal and dermal thickness, and a reduction in the number of superficial goblet cells, occur in the skin of maturing male brown trout. These changes are correlated with rising levels of plasma 11-ketotestosterone and it is suggested that control of integumental structure in male fish is mediated by androgenic steroids during sexual maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb04315.x
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