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  • 1
    Electronic Resource
    Electronic Resource
    Determination of anisotropy fields in recording media (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5711-5713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work describes an experimental study which reviews the various techniques that can be used for determination of anisotropy fields in recording media. At the present time this topic is of considerable importance due to the need to understand the detailed mechanisms of magnetization reversal and the factors that control the switching field distribution in recording media. We have used a metal-particle-based tape material and have employed various magnetic techniques for the determination of the apparent anisotropy field, HK. The techniques included hysteresis loops measured in a direction transverse to the texture direction of the tapes, single-point detection in the successive derivatives of the magnetization with respect to the field, transverse susceptibility measurement, and the variation of the bulk coercivity with temperature. We find the temperature variation of coercivity produces values of HK far smaller than values determined by other methods due to orientation effects. General agreement is seen for the other techniques mentioned and results for samples with differing degrees of texture show that the apparent anisotropy field of the grains as measured by these techniques is influenced greatly by orientation effects. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372498
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  • 2
    Electronic Resource
    Electronic Resource
    Incongruent estimates of population differentiation among brook charr, Salvelinus fontinalis, from Cape Race, Newfoundland, Canada, based upon allozyme and mitochondrial DNA variation (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We determined the amount and temporal stability of genetic differentiation among brook cham sampled from five rivers on Cape Race, Newfoundland, with an electrophoretic analysis of 42 protein coding loci. Fish from four of these rivers were analysed for restriction fragment length polymorphisms in mitochondrial DNA (mtDNA). A single mtDNA clone was observed in all rivers sampled, except one, where 47% offish were from a different and relatively divergent clone (0.31 % sequence divergence). In contrast, Cape Race brook charr show large amounts of genetic differentiation at six enzyme coding loci; Nei's genetic distance ranged between 0,020 and 0.048. This differentiation is relatively stable as no significant differences in allele frequencies were detected between fish sampled from two rivers over two consecutive years. The most divergent population based on protein polymorphism is not that with two mtDNA clonal lineages. In contrast to the commonly held view, mtDNA analyses do not necessarily provide greater resolution of population structure than allozyme analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb05070.x
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  • 3
    Electronic Resource
    Electronic Resource
    Microgeographic population structure of brook charr: a comparison of microsatellite and mark-recapture data (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Polymorphism at five microsatellite genetic markers (genotyped n = 496) and mark-recapture tagging data (tagged n = 9813) were used to define the population structure of brook charr, Salvelinus fontinalis from the Indian Bay watershed, Newfoundland, Canada. Despite the absence of physical barriers to migration among lakes, both genetic and tagging data suggest that brook charr in each lake represent reproductively isolated populations. Exact tests comparing allele frequencies, θ (global value = 0·063), Rst (global value = 0·052), individual assignment tests, and Nei's genetic distance provided congruent estimates of population subdivision in agreement with the tagging data (only 2·2% of recaptures were lake-to-lake). The genetic structure of the brook charr populations corresponded with the geographic structure of the drainage basin on a qualitative level, although linear distance over water was not significantly correlated with the tagging data or the genetic distance measures. The agreement between the tagging and the genetic data suggest that microsatellite markers can be useful tools for defining real biological units. The results also suggest that brook charr exhibit microgeographic population structure at the watershed scale, and that this is the scale at which conservation and management of this salmonid might best be implemented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00032.x
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  • 4
    Electronic Resource
    Electronic Resource
    Spawning behaviour and acoustic communication in Atlantic cod (2003)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc
    Journal of fish biology 63 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mating systems are defined by the pattern of matings among individuals in a population, including the number of mates obtained by each female and male, and the duration of pair bonds. Within all mating systems, mate choice, intra-sexual competition, and sperm competition may lead to variation in mating success among individuals. Growing evidence indicates that quantification of the patterns and processes of mating may be critical to understanding population dynamics. Atlantic cod had been fished for hundreds of years and was one of the most important commercial fish species worldwide until the recent collapse of many populations. Despite being of theoretical interest and practical importance, little was known about this species’ reproductive behaviour. Our research employed a quantitative approach to understand causes and consequences of variation in the mating system of Atlantic cod at the individual and population levels. We incorporated both detailed behavioural studies in the laboratory and observations of cod captured in the commercial fishery. Preliminary observations indicate tremendous variation in reproductive behaviour and mating success both within and between populations. Furthermore, variation in reproductive behaviour and mating success appears to be related to the ability of males to produce sound. Knowledge of Atlantic cod spawning behaviour will likely contribute to better understanding of population dynamics and improved ability to predict the impact of fishing on cod populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2003.216af.x
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  • 5
    Electronic Resource
    Electronic Resource
    Mating of anadromous Atlantic salmon, Salmo salar L., with mature male parr (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 31 (1987), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sexually mature male parr successfully mated with female anadromous Atlantic salmon, Salmo salar, in the absence of anadromous males. There was no significant difference between the proportion of eggs fertilized by mature male parr and anadromous males. One of the demographic consequences of our observations is that overfishing could eventually eliminate anadromy in male members of a population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1987.tb05220.x
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  • 6
    Electronic Resource
    Electronic Resource
    Sex-biased dispersal in a salmonid fish: implications for growth rate and survival (2003)
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc
    Journal of fish biology 63 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: I tested the hypothesis that dispersal is sex-biased in an unexploited population of brook trout (Salvelinus fontinalis Mitchill). Based on the assumptions that trout are promiscuous and that reproductive success is limited primarily by either number of mates (males) or fecundity (females), I predicted that males would disperse greater distances than females. I also tested the hypothesis that trout populations comprise stationary and mobile individuals, predicting that males have greater mobility than females. Based on a 5-year, mark-recapture study of almost 1000 fish, there was strong support for the hypothesis of male-biased dispersal. On average, males dispersed 2·5 times as far as females; during the spawning period only, male dispersal exceeded that by females almost four-fold. Both sexes were heterogeneous with respect to movement, with a lower incidence of mobility among females than males. Sex differences in dispersal may have been responsible for sex biases in seasonal growth. Importantly, growth rate was positively associated with survival, independent of the effects of body size. Sex-biased dispersal may (1) reduce mate competition among male kin, (2) decrease the probability that males will reproduce with related females, and (3) have important implications for life history.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2003.0216q.x
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of population decline, fishing, and spawner variability on the recovery of marine fishes (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 59 (2001), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Based on an analysis of 90 marine fish populations, collapses (the greatest proportional reduction in spawner biomass over 15 years) are predicated typically by dramatic increases in fishing mortality and recoveries are more likely to occur when exploitation is reduced. However, among populations for which fishing mortality declined after collapse, recovery was independent of exploitation rate, even when fishing mortality (F) post-collapse was expressed as a function of each population's maximum growth rate (r). After a period of 15 years, many populations that experienced 15 year declines 〉60% exhibited little or no recovery, despite considerable reductions in fishing mortality. This suggests that factors other than fishing may be considerably more important to recovery, and fishing less important, than previously thought. Furthermore, among populations for which fishing mortality decreased post-collapse, rate of population decline was a reliable predictor of recovery. With the possible exception of clupeids, variation in marine fish breeding population size was found to differ little from that of other vertebrates, and such variability appears to have no effect on rate of recovery. In addition to providing an empirical framework for the study of population collapse and recovery, the analyses presented here provide a means of assessing the precautionary nature of various population-decline thresholds used to assign extinction risks to marine fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb01392.x
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  • 8
    Electronic Resource
    Electronic Resource
    Consequences to fitness-related traits of hybridization between farmed and wild Atlantic salmon, Salmo salar (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Introgression between wild and farmed Atlantic salmon Salmo salar has been hypothesized to influence the persistence of wild populations, particularly those at heightened risk of extinction. Based on pure and hybrid crosses involving one farmed and two wild populations (Tusket River and Stewiacke River, an endangered population) in a common-garden environment, we examined the consequences of introgression to survival, growth, and disease resistance in the first year of life. Introgression with farmed salmon had either no effect (Stewiacke) or a negative effect (Tusket) on survival. Importantly, the among-family variance in survival (a negative correlate of population persistence) was higher for the hybrids than it was among the pure crosses. There was also evidence of genetic differences in growth rate and disease susceptibility. Introgression with their farmed counterparts is unlikely to have a positive effect on the fitness of wild Atlantic salmon. The degree to which genetic interactions between farmed and wild salmon threaten the latter's persistence almost certainly depends on the degree to which individuals are adapted to their local environment, on the genetic differentiation between farmed and wild individuals, and on the relative proportions of farmed and wild salmon during spawning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.0559n.x
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of sex, body size, and reproduction on overwinter lipid depletion in brook trout (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Expressed as percentages of total fresh body weight, lipids of brook trout Salvelinus fontinalis declined between October and April: reproductive males from 2·89 to 1·22%, reproductive females from 3·19 to 1·84%, and non-reproductive males and females from 2·75 to 2·08%. The absolute and proportional overwinter reduction in lipids among reproductive trout was more than twice that of non-reproductive trout, with reproductive males losing significantly more lipids than reproductive females. Larger reproductive individuals lost more lipids during winter, relative to body size, than smaller individuals, although such an effect was not evident among non-reproductive trout. The average overwinter reduction in lipids for reproductive males (58%), females (42%), and non-reproductive trout (24%) was negatively associated with mark-recapture estimates of overwinter survival probabilities of 0·27, 0·36, and 0·58, respectively, providing support for the hypothesis that energy is allocated to reproduction to the detriment of post-reproductive survival. Our emergent hypothesis that reproductive costs differ between sexes, and the life history consequences thereof, merit further study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00737.x
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  • 10
    Electronic Resource
    Electronic Resource
    Mating success of alternative maturation phenotypes in male Atlantic salmon, Salmo salar (1988)
    Springer
    Oecologia 75 (1988), S. 169-174 
    Details
    ISSN: 1432-1939
    Keywords: Frequency-dependent selection ; Parr maturation ; Salmo salar ; Mating strategies ; Canada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mature male parr successfully fertilized eggs of anadromous female Atlantic salmon, Salmo salar, in competition with anadromous males under simulated natural conditions. Mating situations were created in which mature male parr and anadromous males competing for the opportunity to spawn with an anadromous female differed in allelic forms of the same enzyme. Females deposited eggs into a sequence of 3 or 4 eggs nests. The mean proportion of eggs in a redd fertilized by parr increased with increasing numbers of parr present at a redd, reaching 23% at male parr: anadromous male ratios of 20:1. Single male parr fertilized, on average, 5% of the eggs in a redd. The proportion of eggs in an egg nest fertilized by parr also depended upon the order of egg nest construction, such that parr mating success was highest at the initial nest constructed and lowest at the final nest. Parr have relatively high fertilization success for their size when compared with the smaller maturation phenotype of other salmonids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378593
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