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  • 1
    Electronic Resource
    Electronic Resource
    Reproduction of interspecific hybrids of Atlantic salmon and brown trout in a stream environment (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Reproduction between Atlantic salmon males and interspecific hybrid Salmo salar × Salmo trutta females was monitored in a controlled flow channel diverted from a south European river located at the edge of Atlantic salmon natural geographic distribution in Europe.2. Post-F1 hybrids were viable and survived in the wild, at least until dispersal from redds. After transfer to hatchery conditions, 67% survived into the second year.3. The hybrids possessed 98 chromosomes: two sets of Atlantic salmon(2n = 58) and one set of brown trout (n = 40) chromosomes.4. The existence of a low proportion of allotriploid individuals can be expected in rivers where Atlantic salmon and brown trout populations coexist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01068.x
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  • 2
    Electronic Resource
    Electronic Resource
    A Matrix Model to Study the Colonization by Brown Trout of a Virgin Ecosystem in the Kerguelen Islands (1998)
    Springer
    Acta biotheoretica 46 (1998), S. 253-272 
    Details
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present a matrix model for the study of the population dynamics of brown trout Salmo trutta L., introduced in the '60s in the virgin aquatic ecosystems of the Kerguelen Islands. This species clearly acclimatized very well: a portion of the population became migratory and spent a part of its life cycle in the sea, which allowed the rapid colonization of two rivers close to the stream of origin in the same bay (Baie Norvégienne). These migratory trout can become a smolt at 2, 3, or 4 years of age. The model takes into account age and smolt age structures and in a first step considers the fish from the Baie Norvégienne as belonging to a single population. The transition matrix looks like a 32 × 32 Leslie matrix in which some survival rates are not on the subdiagonal. They represent survival after the first sea migration and are particularly important for the dynamics of the whole population. The estimate of demographic parameters was obtained from a data base containing information collected in the field since 1970. The model was calibrated on the population size estimate and the stock structure of the migratory trout in 1979. Population size was estimated by tagging-recapture and monitoring of the migratory trout in freshwater when they returned to overwinter or reproduce. Under the hypothesis of a constant survival rate for all ages and categories of fish, it was possible to determine relationships between the annual population growth rate and survival rates at first downstream migration, for which no direct estimate was available. These constraints on the model induced paradoxical results. For instance, an increase in survival rate reduced migratory trout numbers in the first years of colonization. These data suggested that the average survival rate should be around 0.3 and not 0.5 as surmised in previous studies. However, the model systematically underestimated numbers of migratory trout during the first years of development. Thus, to improve the model it will be necessary to introduce survival rates varying with time. Another possible approach would be to consider the population as three subunits corresponding to the three colonized rivers of the Baie Norvégienne.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001789211146
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Nest Placement and Egg Distribution in Atlantic Salmon Redds (2000)
    Springer
    Environmental biology of fishes 57 (2000), S. 37-47 
    Details
    ISSN: 1573-5133
    Keywords: Salmo salar ; grilse ; nest depth ; nest location ; egg survival ; redd morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Atlantic salmon, Salmo salar, deposit their eggs in excavated depressions called nests. These nests are built from downstream to upstream within one or more redds, and each redd corresponds to a continuous area of the streambed disturbed by the female digging activities. Redd topographic measurements and egg excavation were performed to determine number of nests per redd and per female, nest depth, distances between successive nests, number of eggs deposited per nest, and egg survival in nests created by six grilse Atlantic salmon, five spawning in an experimental stream (Lapitxuri channel) and one in a natural stream (Lurgorrieta Creek, a tributary of the Nivelle River in southwest France). All females constructed a single redd, except one which built two redds in the channel. Redd surface area ranged between 2.3 and 5.7 m2. Each redd had a raised mound of gravel or dome under which most of the eggs were located, and an upstream depression or ‘pot’. Based on expected egg-to-juvenile survival rates previously obtained in the Lapitxuri channel and on juvenile recoveries, between 96 and 97% of the eggs deposited in the channel sections were retrieved. Each female constructed 7 to 11 nests over a period of 3 to 5 days. The first three nests had an average burial depth of 12.9 cm (±1.6 SD) which was greater than the last three nests (mean 9.5 cm±2.6 SD). Eggs removed from the first three nests had higher fertility rates (95.5% vs. 87.2%), greater survival (83.5% vs. 63.1%) and lower occurrences of abnormalities (1.9% vs. 5.5%) than those deposited in the last three nests. Typically, the percentage of eggs deposited per female decreased from the first to the last nest, such that the last two to three nests possessed only a small number of scattered eggs. Similar results were observed in the redd located in Lurgorrieta Creek. The adaptive consequences of the topographic features of redds and the egg allocation patterns we found are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007562508973
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    Paper (German National Licenses)
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