Exophiala salmonis. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
B. L. Brady
Keyword(s):  
Atlantic Salmon ◽  
Leaf Litter ◽  
Geographical Distribution ◽  
Salmo Salar ◽  
Giant Cells ◽  
Salvelinus Namaycush ◽  
Granuloma Formation ◽  
Swim Bladder ◽  
Second Year ◽  
The Brain

Abstract A description is provided for Exophiala salmonis. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS AND SUBSTRATA: Salmo clarkii, S. salar, Salvelinus namaycush; Acacia karroo (leaf litter), Araucaria sp. (wood). GEOGRAPHICAL DISTRIBUTION: Widespread. DISEASE: The three epidemics in fish hatcheries described by Carmichael in S. clarkii and Salvelinus 'namaycush' involved infection of the head only, apparently commencing in the brain and spreading to neighbouring tissue. The lesions were of the chronic granulomatous type. Severe losses were caused. The outbreak described by Richards et al. (1978) was in Atlantic salmon, Salmo salar, second year smolts introduced from a hatchery into sea-cages. Fish exhibited abdominal swelling due to kidney enlargement; the posterior kidney was infected in all fish and lesions were sometimes also present in the heart, liver, spleen, pancreas and muscle. Granuloma formation occurred in all affected organs, the amount of fungus present bore little relation to the extent of granuloma formation. Giant cells were present throughout the lesions. In contrast to Carmichael's description, no lesions were found in the brain, nor in the swim bladder or intestines. PATHOGENICITY AND TRANSMISSION: Carmichael (1966) was unable to obtain infection by injection or by allowing fish to swim in water heavily contaminated by the fungus. Richards et al. (1978) noted that in adjacent cages of fish in seawater only one cage was affected by the disease and suspected that infection was via the commercial food supplied.

Variation in Male Parr Maturation Within and Among Populations of Atlantic Salmon, Salmo salar

1986 ◽  
Vol 43 (6) ◽  
pp. 1242-1248 ◽  
Author(s):  
Ransom A. Myers ◽  
Jeffrey A. Hutchings ◽  
R. John Gibson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Fork Length ◽  
Detectable Effect ◽  
Genetic Changes ◽  
Mature Parr ◽  
Total Proportion ◽  
Second Year ◽  
Size Threshold ◽  
Atlantic Salmon Parr

The covariation of growth and maturation in male Atlantic salmon parr, Salmo salar, produces a relationship characterized by a size threshold below which individuals generally do not mature. The threshold of 70–72 mm fork length is evident both within and among populations. Parr maturation can reduce growth during the second year of life by an average of 4.0%. Among-year variation in growth rate affects the yearly incidence of maturation for males at age 1 + but has no detectable effect on the total proportion of male parr maturing in a population. Increases in the proportion of mature parr in the Matamek River, Quebec, can be explained by variation in growth alone; there is no evidence for genetic changes in this population.

Age at Sexual Maturity in Icelandic Stocks of Atlantic Salmon (Salmo salar)

1983 ◽  
Vol 40 (9) ◽  
pp. 1456-1468 ◽  
Author(s):  
Dennis L. Scarnecchia
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Sexual Maturity ◽  
Physical Factors ◽  
Thermal Gradients ◽  
Ocean Temperature ◽  
Growth And Survival ◽  
Atlantic Salmon Salmo Salar ◽  
Life History Pattern ◽  
Second Year

For Icelandic stocks of Atlantic salmon (Salmo salar) in 77 rivers, the combination of June ocean temperature, length of river ascended by the salmon, discharge of the river in July–September, and latitude explained much of the variation in percentages of grilse — 72% for females and 62% for males. For both sexes, percentage of grilse was directly related to ocean temperature but inversely related to length of river, discharge of river, and latitude. For stocks in 23 Southwest Coast rivers, length of river explained 72% of the variation in percentage of females that were grilse. Females in stocks south of the thermal gradients separating Atlantic from Arctic or Polar water tended to return as grilse; females north of the gradients tended to return after more than one winter at sea. The decline in percentages of grilse clockwise from southwestern to northeastern rivers corresponded closely with the decline in June ocean temperatures between these areas. I hypothesize that the salmon stocks have adapted their age at sexual maturity to the length and discharge of the rivers, natural mortality rates during their second year at sea, and average expected ocean temperatures, reflecting conditions for growth and survival, that the smolts encounter. Age at maturity appears not to be a direct causal response to any of these physical factors, and appears best understood only with reference to the entire life history pattern of each stock.

Multiple changes in the brain of Atlantic salmon, Salmo salar, during photoperiodically-induced parr-smolt transformation

Aquaculture ◽  
1994 ◽  
Vol 121 (1-3) ◽  
pp. 289-290 ◽  
Author(s):  
Pierre-Philippe Morin ◽  
J.Geoffrey Eales ◽  
Toshiaki J Hara ◽  
Svante Winberg ◽  
Göran E Nilsson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Atlantic Salmon Salmo Salar ◽  
The Brain

Development, survival, and structural alterations of embryos and alevins of Atlantic salmon, Salmo salar L., continuously exposed to alkaline levels of pH, from fertilization

1980 ◽  
Vol 58 (3) ◽  
pp. 369-377 ◽  
Author(s):  
P. G. Daye ◽  
E. T. Garside
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Hydrogen Ions ◽  
Gradual Decline ◽  
Cumulative Mortality ◽  
Zona Radiata ◽  
Atlantic Salmon Salmo Salar ◽  
Branchial Epithelium ◽  
The Brain ◽  
Degree Of Severity

Embryos of the Atlantic salmon, Salmo salar L., were incubated continuously from fertilization at pH 6.8 (control) and pH 9.0 and 9.5, initially at 6.7 °C but with a gradual decline in the first 5 weeks to 5.0 °C for the remaining 10 weeks of exposure. Subsequently, the alevins were maintained in these environments for 50 days after hatching. Developmental processes and hatching were not affected by these levels of pH. Percentage cumulative mortality of treated embryos, 8%, was approximately that in the controls. Alevin mortality in the control lots was 1.2 and 1.3%. At pH 9.0, cumulative mortality was 0.4%, but at pH 9.5 there was an accelerating increase to 18%, at the termination of observation.Sublethal changes in embryos were confined mostly to cell necrosis and sloughed rudimentary epidermis. Some metaplasia of the brain stem occurred at pH 9.5. Sites and intensity of alterations increased in alevins at pH 9.5, following the loss of the zona radiata. In addition to ongoing injury of epidermis, including mucous cells, deleterious alterations occurred in branchial epithelium, erythrocytes, myocardium, blood vessels of the viscera, liver, brain, and optic lenses. In general, sublethal changes caused by hydroxylions are similar to those caused by excessive hydrogen ions but are somewhat less extensive in the structures affected or in their degree of severity.

scholarly journals Salinity and photoperiod modulate pubertal development in Atlantic salmon (Salmo salar)

2013 ◽  
Vol 220 (3) ◽  
pp. 319-332 ◽  
Author(s):  
Michelle C Melo ◽  
Eva Andersson ◽  
Per Gunnar Fjelldal ◽  
Jan Bogerd ◽  
Luiz R França ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Plasma Levels ◽  
Pubertal Development ◽  
Mrna Levels ◽  
Treatment Groups ◽  
Timing Of Puberty ◽  
The Brain ◽  
Spermatogonial Proliferation ◽  
Stimulation Of

The Atlantic salmon shows substantial life cycle plasticity, which also applies to the timing of puberty. While it is characterized by the activation of the brain–pituitary–gonad axis, many morphophysiological aspects of puberty and the influence of environmental conditions, such as water salinity, are not well understood in fish. Here, 12-month-old Atlantic salmon coming from an out-of-season smoltification regime in December were exposed to freshwater (FW) or seawater (SW) at 16 °C to stimulate puberty under a 24-h constant light (LL) or 12 h light:12 h darkness (LD) photoperiod. These four treatment groups (FWLL, SWLL, FWLD, and SWLD) were studied from January to March. Next to 11-ketotestosterone (11-KT) plasma levels, the expression of pituitary genes (gnrhr4, fshb, and lhb) and spermatogenesis was quantified. When spermatogonial proliferation started, fshb mRNA levels increased steeply and began to decrease when spermatogonial mitosis approached completion and most germ cells had reached meiotic or post-meiotic stages. Conversely, lhb mRNA levels increased progressively during spermatogenesis. Most males in all treatment groups matured, but exposure to SW resulted in the strongest stimulation of the onset of spermatogenesis and elevation of pituitary gnrhr4 and fshb mRNA levels. Later on, the LD photoperiod accelerated, irrespective of the salinity, the completion of spermatogenesis, associated with higher lhb mRNA and 11-KT plasma levels than in the LL groups. We find that both salinity and photoperiod modulated different aspects of spermatogenesis, and resulted in a differential activation of pituitary and testis functions; SW stimulating the onset and the shorter photoperiod the completion of spermatogenesis.

A model for estimating mortality of Atlantic salmon, Salmo salar, between spawning events

2011 ◽  
Vol 68 (9) ◽  
pp. 1635-1650 ◽  
Author(s):  
P. Bradford Hubley ◽  
A. Jamie F. Gibson
Keyword(s):  
Time Series ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Mortality Rates ◽  
Estimation Model ◽  
Mortality Estimation ◽  
Atlantic Salmon Salmo Salar ◽  
The North ◽  
Second Year ◽  
The North Atlantic Oscillation

We developed a Bayesian hierarchical model to estimate annual mortality of repeat-spawning Atlantic salmon, Salmo salar, that distinguishes between mortality rates and the confounding effects of consecutive-year and alternate-year repeat-spawning strategies. The model provides annual estimates of two mortality rates: mortality in the first year (Z1), a time period during which salmon are primarily in freshwater (staging, spawning, and overwintering) followed by a brief period at sea, and mortality in the second year (Z2) when salmon are predominantly at sea. When fit to data for the LaHave River (Nova Scotia, Canada) salmon population, Z1 showed an increasing trend throughout the time series, whereas Z2 also increased but in a single, stepwise manner. Once a time series of mortality rates was separated from the other life-history parameters, we were able to demonstrate how they could be used for examining the influence of environmental conditions by comparing the estimated mortality rate time series with the North Atlantic Oscillation Index (NAOI). This comparison uncovered a statistically significant correlation between the NAOI and the survival in the second year after spawning that would not have been evident had the mortality estimation model not been developed.

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