scholarly journals Utilization of brown troutSalmo truttabyAcanthocephalus clavulain an Irish lake: is this evidence of a host shift?

2004 ◽  
Vol 78 (3) ◽  
pp. 201-206 ◽  
Author(s):  
C.J. Byrne ◽  
C.V. Holland ◽  
E. Walsh ◽  
C. Mulligan ◽  
C.R. Kennedy ◽  
...  
Keyword(s):  
Population Biology ◽  
Salmo Trutta ◽  
Anguilla Anguilla ◽  
Host Shift ◽  
Reproductive Maturity ◽  
Large Numbers ◽  
Host Diet ◽  
Potential Competitor ◽  
The Mean ◽  
Accidental Host

AbstractThe population biology of the fish acanthocephalanAcanthocephalus clavulawas described from 161 wild brown trout,Salmo truttasampled over a two-year period in Clogher Lake in the west of Ireland. Overall prevalence of the parasite was 86% and the mean abundance was 53 worms per fish. Despite the presence of large numbers of worms in the trout very few females (2%) attained full reproductive maturity. This suggests that trout is an accidental host. A sample of yellow eels,Anguilla anguillawas examined at a different time from the same lake. The prevalence ofA. clavulawas 97% and the average abundance was 8 worms per fish. In contrast to the situation in trout, the proportion of female worms attaining full reproductive maturity was 61% fulfilling the expected characteristic of a preferred definitive host. The possible explanations for the very high abundance ofA. clavulain trout are discussed and include the influence of fluctuations in host populations, host diet and the absence of a potential competitor.

Studies on Crepidostomum metoecus (Braun) and C. farionis (Müller), parasitic in Salmo trutta L. and S. salar L. in Britain

Parasitology ◽  
1958 ◽  
Vol 48 (3-4) ◽  
pp. 336-352 ◽  
Author(s):  
J. D. Thomas
Keyword(s):  
Salmo Trutta ◽  
Anguilla Anguilla ◽  
Habitat Isolation ◽  
Acquired Immunity ◽  
Host Fish ◽  
Individual Fish ◽  
Large Numbers ◽  
Accidental Host ◽  
Fish Hosts ◽  
First Time

1. Crepidostomum farionis (Müller, 1784) and C. metoecus (Braun, 1900) were found to occur together in the same host fish, Salmo trutta L., S. salar L. and Anguilla anguilla (L.) in mid-Wales. It is believed that the latter species constituted an accidental host.2. C. metoecus is recorded in Britain for the first time.3. There was some evidence of a habitat isolation in individual fish as C. metoecus occurred predominantly within the pyloric caeca, while C. farionis usually occupied a more posterior station in the intestine.4. A detailed description is given of G. metoecus and the salient features of this species are compared with those of C. farionis.5. The two species of Crepidostomum commonly occurred in large numbers in their fish hosts, individual fish harbouring up to 157 worms. No lesions attributable to Crepidostomum were, however, detected and there was no evidence of pathogenicity.6. It would appear that the eel is physiologically immune to both species of Crepidostomum and that the salmon parr is partially resistant.7. The degree of infestation of trout and parr with both the Crepidostomum species is at a maximum during the winter months and at a minimum in the summer months. This seasonal variation can be attributed to a periodicity in the swarming of the cercariae.8. There is no evidence of age resistance or acquired immunity of the trout to infestation by Crepidostomum species.

scholarly journals Growth and population biology of the sand-bubbler crab Scopimera crabricauda Alcock 1900 (Brachyura: Dotillidae) from the Persian Gulf, Iran

2021 ◽  
Vol 82 (1) ◽  
Author(s):  
Sana Sharifian ◽  
Vahid Malekzadeh ◽  
Ehsan Kamrani ◽  
Mohsen Safaie
Keyword(s):  
Persian Gulf ◽  
Population Biology ◽  
Slow Growth ◽  
Carapace Width ◽  
Population Data ◽  
Natural Mortality ◽  
Frequency Distributions ◽  
Iranian Coast ◽  
The Mean ◽  
The Persian Gulf

Abstract Background Dotillid crabs are introduced as one common dwellers of sandy shores. We studied the ecology and growth of the sand bubbler crab Scopimera crabricauda Alcock, 1900, in the Persian Gulf, Iran. Crabs were sampled monthly by excavating nine quadrats at three intertidal levels during spring low tides from January 2016 to January 2017. Results Population data show unimodal size-frequency distributions in both sexes. The Von Bertalanffy function was calculated at CWt = 8.76 [1 − exp (− 0.56 (t + 0.39))], CWt = 7.90 [1 − exp (− 0.59 (t + 0.40))] and CWt = 9.35 [1 − exp (− 0.57 (t + 0.41))] for males, females, and both sexes, respectively. The life span appeared to be 5.35, 5.07, and 5.26 years for males, females, and both sexes, respectively. The cohorts were identified as two age continuous groups, with the mean model carapace width 5.39 and 7.11 mm for both sexes. The natural mortality (M) coefficients stood at 1.72 for males, 1.83 for females, and 1.76 years−1 for both sexes, respectively. The overall sex ratio (1:0.4) was significantly different from the expected 1:1 proportion with male-biased. Recruitment occurred with the highest number of annual pulse once a year during the summer. Conclusions The results, which show slow growth, emphasize the necessity of proper management for the survival of the stock of S. crabricauda on the Iranian coast of the Persian Gulf.

scholarly journals Relaxation Times in Strictly Disk Systems

1971 ◽  
Vol 10 ◽  
pp. 15-19
Author(s):  
George B. Rybicki
Keyword(s):  
Numerical Experiments ◽  
Relaxation Times ◽  
Galactic Structure ◽  
Large Numbers ◽  
Order Of Magnitude ◽  
Vlasov Limit ◽  
The Mean ◽  
Gravitating Systems

AbstractIt is shown that the time of relaxation by particle encounters of self-gravitating systems in the plane interacting by 1/r2 forces is of the same order of magnitude as the mean orbit time. Therefore such a system does not have a Vlasov limit for large numbers of particles, unless appeal is made to some non-zero thickness of the disk. The relevance of this result to numerical experiments on galactic structure is discussed.

Variation within and between Rivers in Adult Size and Sea Age at Maturity of Anadromous Brown Trout, Salmo trutta

1991 ◽  
Vol 48 (6) ◽  
pp. 1015-1021 ◽  
Author(s):  
Jan Henning L'Abée-Lund
Keyword(s):  
Brown Trout ◽  
Sexual Maturity ◽  
Salmo Trutta ◽  
Adult Size ◽  
Age At Maturity ◽  
Migration Distance ◽  
Spawning Area ◽  
Brown Trout Salmo Trutta ◽  
Males And Females ◽  
The Mean

I compared adult size and sea age at sexual maturity among nine populations of anadromous brown trout, Salmo trutta, in two Norwegian rivers to determine the extent of inter- and intrariverine variations. Variation in the mean length of spawners and in the mean sea age at sexual maturity were mainly dependent on the variations found within rather than between rivers. Mean lengths and mean age at maturity of males increased significantly with increasing altitude of the spawning area and with migration distance in freshwater. In females, positive significant correlations were found with mean lengths and altitude of the spawning area and with mean sea age at maturity and both spawning site altitude and migration distance. Mean lengths and ages of males and females were not significantly correlated with the rate of water discharge in the streams during spawning. The size of gravel substrate for spawning was of minor importance in explaining interpopulation variation in mean female size. The increase noted in mean length and in mean sea age at maturity of both males and females is probably an adaptation to greater energy expenditure to reach the uppermost natal spawning areas.

GLOBAL FLUCTUATIONS FOR LINEAR STATISTICS OF β-JACOBI ENSEMBLES

2012 ◽  
Vol 01 (04) ◽  
pp. 1250013 ◽  
Author(s):  
IOANA DUMITRIU ◽  
ELLIOT PAQUETTE
Keyword(s):  
Gaussian Process ◽  
Covariance Matrix ◽  
Law Of Large Numbers ◽  
Test Functions ◽  
Linear Statistics ◽  
Jacobi Ensemble ◽  
Large Numbers ◽  
The Mean ◽  
Shifted Chebyshev Polynomial ◽  
Global Fluctuations

We study the global fluctuations for linear statistics of the form [Formula: see text] as n → ∞, for C1 functions f, and λ1, …, λn being the eigenvalues of a (general) β-Jacobi ensemble. The fluctuation from the mean [Formula: see text] turns out to be given asymptotically by a Gaussian process. We compute the covariance matrix for the process and show that it is diagonalized by a shifted Chebyshev polynomial basis; in addition, we analyze the deviation from the predicted mean for polynomial test functions, and we obtain a law of large numbers.

scholarly journals Limit Theorems and Fluctuations for Point Vortices of Generalized Euler Equations

2021 ◽  
Vol 182 (3) ◽  
Author(s):  
Carina Geldhauser ◽  
Marco Romito
Keyword(s):  
Euler Equations ◽  
Mean Field ◽  
Point Vortices ◽  
Positive Temperature ◽  
Field Limit ◽  
Mean Field Limit ◽  
Large Numbers ◽  
The Mean ◽  
Formal Solutions ◽  
2D Torus

AbstractWe prove a mean field limit, a law of large numbers and a central limit theorem for a system of point vortices on the 2D torus at equilibrium with positive temperature. The point vortices are formal solutions of a class of equations generalising the Euler equations, and are also known in the literature as generalised inviscid SQG. The mean-field limit is a steady solution of the equations, the CLT limit is a stationary distribution of the equations.

scholarly journals Documentation of multiple species of marine fish trapped in Atlantic salmon sea-cages in Norway

2018 ◽  
Vol 31 ◽  
pp. 31
Author(s):  
Per Gunnar Fjelldal ◽  
Monica F. Solberg ◽  
Kevin A. Glover ◽  
Ole Folkedal ◽  
Jonatan Nilsson ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Salmo Trutta ◽  
Gadus Morhua ◽  
Mesh Size ◽  
Anguilla Anguilla ◽  
Wild Fish ◽  
Melanogrammus Aeglefinus ◽  
European Eel ◽  
Farmed Salmon ◽  
Sea Trout

The production of salmonids in sea-cages has been developed for monoculture of the target species. However, we show here for the first time, that wild fish may enter sea-cages used for farming of Atlantic salmon (Salmo salar L.) in Norway, out-grow the mesh size, and thereafter become permanently trapped. Within seven different sea-cages located in western Norway, eight different species of wild fish were identified; European eel (Anguilla anguilla), sea trout (Salmo trutta L.), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), pollack (Pollachius pollachius), hake (Merluccius merluccius) and whiting (Merlangius merlangus). In the two most extreme cases, a 5 × 5 × 7 m cage with 311 farmed salmon (903 g) also contained 542 whiting (79 g), 77 haddock (43 g), and 5 cod (26 g), and a 12 × 12 × 15 m cage with 1695 farmed salmon (559 g) also contained 1196 haddock (35 g), 1115 whiting (31 g), 46 cod (23 g), 23 saithe (48 g), 15 pollock (22 g), 5 sea trout (54 g), and 2 hake (29 g). The present study thus demonstrates that aquaculture cages designed for monoculture may attract and effectively ‘trap’ wild fish. We did not investigate the frequency of this occurrence, and the ecological significance of these observations remains unclear. However, with the ever-increasing number of sea-cages used for global aquaculture, this is clearly a topic for further research.

ASYNCHRONOUS UPDATING RESTORES THE LAW OF LARGE NUMBERS IN GLOBALLY COUPLED SYSTEMS

2002 ◽  
Vol 12 (03) ◽  
pp. 663-669 ◽  
Author(s):  
SUDESHNA SINHA
Keyword(s):  
Law Of Large Numbers ◽  
Mean Field ◽  
Coupled Systems ◽  
Large N ◽  
Large Numbers ◽  
Statistical Behavior ◽  
Remarkable Result ◽  
Asynchronous Updating ◽  
The Mean ◽  
The Law

It was observed in earlier studies, that the mean field of globally coupled maps evolving under synchronous updating rules violated the law of large numbers, and this remarkable result generated widespread research interest. In this work we demonstrate that incorporating increasing degrees of asynchronicity in the updating rules rapidly restores the statistical behavior of the mean field. This is clear from the decay of the mean square deviation of the mean field with respect to lattice size N, for varying degrees of asynchronicity, which shows 1/N behavior upto very large N even when the updating is far from fully asynchronous. This is also evidenced through increasing 1/f2 behavior regimes in the power spectrum of the mean field under increasing asynchronicity.

The growth of Moniliformis (Acanthocephala) in rats fed on various monosaccharides and disaccharides

1980 ◽  
Vol 209 (1175) ◽  
pp. 299-315 ◽  
Keyword(s):  
Intestinal Tract ◽  
Anterior Part ◽  
Reproductive Activity ◽  
Dry Mass ◽  
Female Rats ◽  
Male And Female ◽  
Male And Female Rats ◽  
Host Diet ◽  
The Mean ◽  
Growth And Reproduction

Aspects of the course of infection, growth and reproductive activity of Moniliformis were studied in adult male and female rats fed on iso -energetic purified diets containing various sugars. When rats were infected and fed on experimental diets containing either 3% glucose or 3% galactose for 5 weeks, very little growth of the worms and no signs of reproduction were observed. In contrast, Moniliformis grew well and showed many signs of normal reproduction when the rats were fed on diets containing either 3% fructose or 3% mannose. The ability of the worms to grow and reproduce was not lost by maintaining them first for 5 weeks in rats fed on diets containing 3% glucose and 3% galactose. When the diets of such rats were changed to ones containing 3% starch and 3% fructose, respectively, for a further 5 weeks, the worms grew and normal reproduction occurred. Similar experiments were carried out in which groups of infected rats were fed for 5 weeks on diets containing gradually increasing amounts of glucose (6-36%). It was not until the rats were fed on diets containing 24% glucose that the mean dry mass of the worms approached that of worms from rats fed on the diet con­taining 3% fructose; no host diet was found to be as effective a supporter of worm growth as 3% mannose. Under no circumstances, not even when the host’s diet contained 36%, was galactose found to be a suitable sugar for supporting the growth and reproduction of Moniliformis . Results consistent with those recorded for worms from rats fed on the diets containing monosaccharides were obtained when infected rats were fed for 5 weeks on diets containing 3% of various disaccharides. Considerable growth and reproduction of Moniliformis occurred when sucrose was included in the host’s diet, but not when lactose, maltose or trehalose was present. Several of these observations may be related to the fact that different sugars are absorbed at different rates from the intestinal tract. It is suggested that all of a given sugar, when present in the diet at a low concentration, may be removed rapidly from the anterior part of the small intestine with the result that none will be available to the parasites. Significant amounts, however, of those sugars that are absorbed more slowly may reach the region of the intestine in which the parasite normally lives.

POWDERY MILDEW RESISTANCE IN STRAWBERRY PROGENIES

1961 ◽  
Vol 41 (2) ◽  
pp. 239-243 ◽  
Author(s):  
Hugh A. Daubeny
Keyword(s):  
Powdery Mildew ◽  
Powdery Mildew Resistance ◽  
Breeding Program ◽  
Mildew Resistance ◽  
Large Numbers ◽  
The Mean ◽  
Strawberry Breeding ◽  
Resistance Rating

The effect of various parents on the degree of powdery mildew resistance in strawberry progenies was studied. Puget Beauty parentage, compared with Siletz, Surecrop, Talisman, Magoon, or Stelemaster parentage, gave a highly significant increase in the mean resistance rating. British Sovereign parentage, compared with Northwest or Agassiz parentage, gave a significant increase in the mean resistance rating. Puget Beauty was the only parent to give relatively large numbers of seedlings immune or resistant to powdery mildew. Siletz was as resistant to the disease as Puget Beauty, but did not transmit this resistance to its progeny. Selections immune or resistant to powdery mildew will be used in the strawberry breeding program at Agassiz.

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