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  • 1
    Digitale Medien
    Digitale Medien
    Assessment of winter size-selective mortality of young-of-the-year Atlantic salmon (Salmo salar) using otolith microstructure analysis (2005)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 14 (2005), S. 0 
    Details
    ISSN: 1600-0633
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract –  The objectives of this study were, first, to assess the usefulness of otolith microstructure analysis to examine winter size-selective mortality of young-of-the-year (YOY) Atlantic salmon and, secondly, to validate various hypotheses relating to the dynamics of two populations with different winter survival. By examining otolith microstructure, we back-calculated body size at hatching and at emergence of YOY salmon sampled in fall 2000 and in early summer 2001 on the Petite Cascapédia River and the Bonaventure River (Québec, Canada). The results of the study did not reveal any size-selective mortality of YOY salmon in the Petite Cascapédia River, while in the Bonaventure River, size-selective mortality of the smaller individuals of the cohort was detected. This case study allowed not only a better comprehension of the population dynamics of those rivers but demonstrated the usefulness of otolith analysis to detect winter size-selective mortality under a natural environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0633.2005.00089.x
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  • 2
    Digitale Medien
    Digitale Medien
    Quantifying the effectiveness of regional habitat quality index models for predicting densities of juvenile Atlantic salmon (Salmo salar L.) (2004)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 13 (2004), S. 0 
    Details
    ISSN: 1600-0633
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract –  The suitability of using regional Habitat Quality Index (HQI) models for predicting distributions of juvenile salmon (Salmo salar L.) was examined using data acquired from selected rivers within Québec, Canada. Regional HQI models were derived by identifying preferences of salmon fry and parr for the habitat properties of flow velocity, water column depth and granulometric index (an index of substrate size) for groups of rivers. These were compared with local HQI models, derived from preferences for habitat properties within individual rivers. Relationships between HQI values and densities of juvenile salmon were established through the use of nonlinear regression. In all cases, the regional HQI models were less effective for explaining distributions of juvenile salmon than local HQI models based on individual rivers. Regional HQI models were relatively ineffective when the habitat characteristics of the river to which they were applied differed greatly from the characteristics of the other rivers within the region. It is inferred that the relationship between the effectiveness of the regional HQI model and the difference in characteristics between individual rivers and those of the region may be used in an a priori determination of whether a regional HQI may be applied effectively to any given river.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0633.2004.00069.x
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  • 3
    Digitale Medien
    Digitale Medien
    Determination of the age of young American eels, Anguilla rostrata, in fresh water, based on otolith surface area and microstructure (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 32 (1988), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The time elvers of the American eel, Anguilla rostrata, spend in an estuary prior to their migration into fresh water was assessed. A distinct mark was formed on elvers' otoliths during their first 2 to 3 weeks in the river estuary. This mark was used to distinguish between growth in fresh water and in salt water. Migrating eels collected at a falls 4 km from the estuary exhibited bimodal length and weight distributions. Frequency distributions showed that eels collected in the estuary were smaller and had smaller otoliths than eels collected at the falls, indicating that elvers do not reach the falls in the same year as they enter the estuary. The three modal groups most probably represent three age–classes. However, the otoliths of elvers collected in the estuary had only the mark of transition whereas eels in the first and second mode at the falls usually had two rings (1–4) and four rings (3–6) per otolith, respectively, in addition to the mark of transition, as viewed under SEM. The possibility that ring formation is not annual means that the use of otoliths for the age determination of eels in this study has not been validated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1988.tb05351.x
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  • 4
    Digitale Medien
    Digitale Medien
    Habitat selection by juvenile Atlantic salmon: the interaction between physical habitat and abundance (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 67 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The effect of physical river habitat variables on the distribution of juvenile Atlantic salmon Salmo salar L. in the Rivière de la Trinité, Québec, Canada, was examined using generalized additive modelling. A survey of Atlantic salmon fry and parr densities and habitat variables (flow velocity, water column depth and substratum size) was conducted in the summer months from 1984 to 1992. Clear patterns of habitat use existed: specific ranges of habitat variables were selected, with parr preferring greater velocities, depths and substratum sizes than fry. There was a large variation, however, in juvenile densities for given velocities, depths or substratum sizes, with this variation being greatest in optimal habitats. On examination of an individual year, interaction between the variables was found to explain some of the variation. On a year-to-year basis the juvenile Atlantic salmon population was found to exhibit an ‘Ideal Free Distribution’, which resulted in greatest variation in optimal habitats with year-to-year changes in population abundance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00808.x
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  • 5
    Digitale Medien
    Digitale Medien
    Distinguishing trophic and habitat partitioning among sympatric populations of the estuarine fish Osmerus mordax Mitchill (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 66 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Sympatric populations of rainbow smelt Osmerus mordax of the St Lawrence middle estuary exhibited distinct morphologies suitable for exploiting either pelagic or benthic habitats in the absence of consistent morphological features related to specific diets. The magnitude of morphological differentiation was elevated and constant over 3 years even though statistically significant differences were observed among samples within populations. Both populations were spatially segregated in the estuary but some population mixing occurred at low densities of rainbow smelt. Diet analysis revealed that both populations opportunistically feed on large macrozooplankton. An amended version of Schoener's D was developed and used to compare the magnitude of niche overlap. It revealed that the diet of the middle estuary rainbow smelt differed according to the area where samples were collected but no differences existed between populations. The exploitation of ecologically distinct habitats appeared to be effective in maintaining morphologically distinct sympatric populations within an estuarine setting in the absence of diet differentiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00702.x
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  • 6
    Digitale Medien
    Digitale Medien
    Ontogenetic changes in the longitudinal distribution of two species of larval fish in a turbid well-mixed estuary (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 35 (1989), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The relationship between vertical migration, estuarine retention and species-specific patterns of longitudinal distribution of the pelagic larvae of rainbow smelt, Osmerus mordax, and tomcod, Microgadus tomcod, was investigated in the upper section of the St Lawrence Middle Estuary. We hypothesized that the species-specific use of the vertical pattern of current exhibited by the two species results in the partitioning of the estuarine habitat in the longitudinal plane while assuring retention. Important differences in the longitudinal distribution of tomcod and smelt larvae were related to the ontogeny of their vertical distribution in the water column. In June, small tomcod and smelt larvae are generally associated with waters of salinities less than 5%o. As the larvae grow, their vertical distribution patterns change, leading to a horizontal separation of the two species. Tomcod juveniles migrate downstream into colder, more saline waters, whereas larger smelt larvae migrate upstream into warmer, tidal fresh waters. Ontogenetic changes in vertical distribution serve to concentrate larvae in specific conditions that may optimize physiological conditions and also permit population persistence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1989.tb03044.x
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  • 7
    Digitale Medien
    Digitale Medien
    Population bottlenecks: influence on mitochondrial DNA diversity and its effect in coregonine stock discrimination (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 35 (1989), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: This study was designed to test the hypothesis that anadromous populations of North American whitefish, Coregonus clupeaformis (Mitchill), believed to have suffered more intense population bottlenecks during past glaciation events, should reveal less mitochondrial DNA (mtDNA) variability and population-genetic structuring than anadromous populations of European whitefish, C. lavaretus (L.). C. clupeaformis exhibited extremely low levels of diversity and population structuring, in terms of number and frequency of clonal lines as well as sequence divergence estimates, as compared with populations of C. lavaretus. These results support the hypothesis that the severity of population bottlenecks related to Pleistocene glaciation events may be largely responsible for the level of mtDNA variability observed. This in turn influences the sampling strategy required to maximize the usefulness of mtDNA analysis in stock discrimination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1989.tb03066.x
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  • 8
    Digitale Medien
    Digitale Medien
    Diel activity patterns of juvenile Atlantic salmon in rivers with summer water temperature near the temperature-dependent suppression of diurnal activity (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Direct day and night underwater observations of juvenile Atlantic salmon Salmo salar during summer and autumn showed a duality in response to temperature between 7 and 11° C for young-of-the-year (YOY) Atlantic salmon. They were predominantly diurnal in early summer and nocturnal in late summer although water temperatures were similar. Post-YOY Atlantic salmon did not show a strong response to temperature as they were mostly nocturnal during the study period. It is suggested that the difference in activity patterns between YOY and post-YOY Atlantic salmon can be explained by size-dependent trade-off between growth and predation risk.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00532.x
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  • 9
    Digitale Medien
    Digitale Medien
    Genetic structure and relationships among anadromous and landlocked populations of rainbow smelt, Osmerus mordax, Mitchill, as revealed by mtDNA restriction analysis (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Larvae of anadromous rainbow smelt originating in various spawning tributaries are retained in the St Lawrence estuary. We proposed that these smelt represent one population genetically differentiated from adjacent populations characterized by geographically distinct larval retention areas. We also analysed four landlocked populations to evaluate the phylogenetic basis of dwarf and normal-sized phenotypes and their relation to an adromous smelt. A phylogenetic distinction was revealed between anadromous and landlocked smelt, with only one of the two mtDNA phylogenetic groups of anadromous fish observed among landlocked smelt. Significant geographical heterogeneity in the distribution of mtDNA genotypes was observed among landlocked smelt, suggesting that dwarfism in smelt may be polyphyletic in origin. St Lawrence smelt were genetically identical but distinct from adjacent populations, supporting the proposition that population genetic structure reflects the number of larval retention zones rather than spawning sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb05068.x
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  • 10
    Digitale Medien
    Digitale Medien
    Phylogenetic relationships among the subfamily Coregoninae as revealed by mitochondrial DNA restriction analysis (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Mitochondria1 DNA (mtDNA) restriction analysis was used to assess phylogenetic patterns among 21 taxa of the subfamily Coregoninae. The genus Prosopium formed a very distinct group differing by 10% (sequence divergence estimate) from other species. Coregonus and Stenodus species were closely related, diverging by sequence divergence estimates of less than 5.6%. These species split into two major sister groups. One comprised all ‘true whitefish’ (subgenus Coregonus) and four cisco species (subgenus Leucichrhys). The most distant species within this assemblage was the Acadian whitefish (C. huntsmani). The other group included all other cisco species and also the Inconnu (Stenodus leucichthys). These results supported a polyphyletic origin of the ciscoes, and did not support Stenodus as a sister taxon of the genus Coregonus. The levels of sequence divergence observed suggested that most extant coregonines radiated during the Pleistocene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb05091.x
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