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  • Canadian Science Publishing  (4)
Materialart
Verlag/Herausgeber
  • Canadian Science Publishing  (4)
Sprache
Erscheinungszeitraum
  • 1
    Online-Ressource
    Online-Ressource
    Canadian Science Publishing ; 1999
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 56, No. S1 ( 1999-11-30), p. 26-34
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 56, No. S1 ( 1999-11-30), p. 26-34
    Kurzfassung: We evaluated the costs and benefits of long-distance horizontal migration by pelagic planktivores, Atlantic herring (Clupea harengus), blue whiting (Micromesistius poutassou), mackerel (Scomber scombrus), and capelin (Mallotus villosus) in the Norwegian and Barents seas using a numerical model and tested model predictions against field observations. Specifically, we considered (i) energetic costs as a function of body size, water currents, swimming speed, and distance, (ii) time costs as a function of speed and distance, and (iii) energetic gain in terms of differences in food intake between areas. The model demonstrates how body size restricts large-scale horizontal migration patterns. Model and field results suggest that the extent of migration will increase with increasing body length. The model predicts that long-distance migration costs may exceed energy intake for fish 〈 20 cm, due to increased hydrodynamical drag with decreasing fish size. Field results suggest that migration distance is a function of length, weight, and age. Food abundance and distribution, current speed and direction, and differences in day length at boreal latitudes are believed to be the major driving forces influencing large-scale migration distance, direction, and timing in pelagic planktivores. Northwards latitudinal rather than longitudinal feeding migrations are explained by the improved feeding opportunities with increased day lengths.
    Materialart: Online-Ressource
    ISSN: 0706-652X , 1205-7533
    Sprache: Englisch
    Verlag: Canadian Science Publishing
    Publikationsdatum: 1999
    ZDB Id: 7966-2
    ZDB Id: 1473089-3
    SSG: 21,3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    Canadian Science Publishing ; 1998
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 55, No. 3 ( 1998-03-01), p. 631-638
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 55, No. 3 ( 1998-03-01), p. 631-638
    Kurzfassung: The life history of capelin (Mallotus villosus) is presently suggested to be sex specific: while males follow a semelparous batch-spawning strategy, females are iteroparous. This hypothesis is based on predictions from a life history simulation model of Barents Sea capelin that shows that iteroparity is more profitable than semelparity for females, but for males, semelparity with several matings with females may be as profitable as iteroparity. These predictions are supported by (i) reports of males mating with several females during a spawning season, (ii) males having a lower gonadosomatic index than females and instead spending their energy on mating and somatic growth, and (iii) an observed higher mortality for males after spawning. The Darwinian fitness of female capelin is limited by the amount of eggs they can carry, and offspring production may only be increased by undertaking several spawning seasons with yearly intervals. Added together, these indices suggest that male and female capelin follow different life history strategies.
    Materialart: Online-Ressource
    ISSN: 0706-652X , 1205-7533
    Sprache: Englisch
    Verlag: Canadian Science Publishing
    Publikationsdatum: 1998
    ZDB Id: 7966-2
    ZDB Id: 1473089-3
    SSG: 21,3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Canadian Science Publishing ; 2007
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 64, No. 12 ( 2007-12-01), p. 1747-1760
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 64, No. 12 ( 2007-12-01), p. 1747-1760
    Kurzfassung: We investigate the trade-offs associated with vertical migration and swimming speed of Atlantic cod (Gadus morhua) using an adaptive individual-based model. Simulations with varying distribution and occurrence of prey, with and without swimbladder constraints, and visual predation were performed. Most simulations resulted in cod migrations between the bottom and pelagic zones. In simulations with high probability of encountering pelagic prey, the cod spent the daytime in the pelagic zone, moving to the bottom to feed only when no pelagic prey were encountered. At night the cod stayed in the pelagic zone to attain neutral buoyancy. In simulations with low occurrence of pelagic prey or high visual predation pressure, the cod remained at the bottom feeding on the consistently present benthic prey. If the pelagic prey occurred far above the sea floor or there were no benthic prey, the cod abandoned all bottom contact. The study thus predicts that the probability of encountering energy-rich pelagic prey is the key factor in driving vertical migration in adult cod. Buoyancy regulation is further shown to be an important constraint on vertical migration.
    Materialart: Online-Ressource
    ISSN: 0706-652X , 1205-7533
    Sprache: Englisch
    Verlag: Canadian Science Publishing
    Publikationsdatum: 2007
    ZDB Id: 7966-2
    ZDB Id: 1473089-3
    SSG: 21,3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    Canadian Science Publishing ; 2016
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 73, No. 2 ( 2016-02), p. 177-188
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 73, No. 2 ( 2016-02), p. 177-188
    Kurzfassung: Johan Hjort’s so-called second recruitment hypothesis addressed the fate of offspring that drift out of areas suitable for their survival. This hypothesis has forged the concept of a population as a closed life cycle, making countercurrent adult spawning migration a necessary mechanism in balancing larval drift. The Norwegian spring-spawning (NSS) herring stock (Clupea harengus), the object of much of Hjort’s work, is spread over large areas in the Northeast Atlantic, with spawning along the Norwegian coast, nursery areas in the Barents Sea, feeding areas in the Norwegian Sea, and overwintering areas outside northern Norway. Understanding the spatial dynamics of highly migratory fish stocks such as the NSS herring, therefore, is critical to understanding their population dynamics. Here I review hypotheses on the spatial dynamics of fish focusing on NSS herring and discuss consequences for population dynamics and interactions with other ecosystem components. The results illustrate the key role that strong herring cohorts play both as predators in the Barents and Norwegian seas and as prey on the overwintering and spawning grounds along the Norwegian coast. It is advocated that spatial full life cycle models should be developed for key fish stocks as a meeting place for model assumptions and observations and as a test bed for a multiple hypothesis testing approach.
    Materialart: Online-Ressource
    ISSN: 0706-652X , 1205-7533
    Sprache: Englisch
    Verlag: Canadian Science Publishing
    Publikationsdatum: 2016
    ZDB Id: 7966-2
    ZDB Id: 1473089-3
    SSG: 21,3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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