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  • 1
    Electronic Resource
    Electronic Resource
    Size-dependent mortality of juvenile Atlantic cod, estimated from recaptures of released reared cod and tagged wild cod (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The recapture rate and survival of reared cod Gadus morhua L. (15–45 cm) released in fjords and open coastal areas of Norway increased with increasing size at release, while release area and season also had a significant influence on the results. High mortality soon after release reduced the number of released fish by more than two–thirds within 6 months, and reduced the potential commercial yield to a low level. In most cases the recapture yield was lower than the released biomass and the net yield increased little or not at all with increasing size at release. In western Norway high fishing mortality of young fish reduced the numbers of surviving fish rapidly and the growth overfishing reduced the potential yield still further. Natural mortality decreased with increasing size at release, and became low when the fish approached their size refuge, i.e. when they could not be eaten by their usual predators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00766.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative analysis of stomach contents of cultured and wild cod, Gadus morhua L. (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 23 (1992), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In a cod enhancement project in a small fjord in western Norway, two groups of reared cod, Gadus morhua L., were released with 6 months’difference in time. After the last release a 3-week fishing survey was conducted. Stomachs from wild and recaptured reared cod of similar size were sampled and analysed. The last released cod had learned to catch the same prey types and in the same relative proportions as the wild cod the second week after release, but mean weight of stomach contents and mean numbers of prey items per stomach were smaller, and a larger proportion of the newly released fish had empty stomachs. Three weeks after release the proportion of empty stomachs was similar to that of wild cod and the first released reared cod, but the food intake was still smaller. The first released group of reared cod, which had spent 6 months in the fjord, seemed to feed as efficiently on wild prey as did wild cod.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.1992.tb00809.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of size-selective mortality on growth of coastal cod illustrated by tagging data and an individual-based growth and mortality model (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 52 (1998), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In a release experiment with cod in Norway, the apparent mean growth rates of 3+ cod, calculated by sampling the released cohorts at different ages, were very slow (〈0·08 mm day−1). However, when individual growth rates of individual tagged cod of the same size range were measured, the mean growth rates were much faster (0·24 mm day−1). These observations were attributed to size-selective fishing mortality and were illustrated by an individual based simulation model of a cohort of cod with variable individual growth rates. The effects on mean length at age of the surviving cohort of increasing fishing intensity were demonstrated. The model showed that size-selective fishing with the observed individual growth variation, removed the fastest-growing individuals at proportionally higher rates than the slower-growing ones, leading to decreased apparent mean growth rate. The fishing pattern which gave the optimum yield, changed when individual variation was included, and when the apparent growth rate was used in the model the yield per recruit reduced dramatically. This study has shown that individual growth heterogeneity and size-selective mortality are factors which should be considered in future fisheries management models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1998.tb00813.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Estimates of larval survival of cod by releases of genetically marked yolk-sac larvae (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 51 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the spring of 1995, 18 million genetically marked yolk-sac cod larvae Gadus morhua were released into a 2.9-km2, nearly land-locked fjord in western Norway. Four quantitative surveys were conducted, 11, 33, and 63 days, and 1 year after the first release. Almost 100% of the collected cod larvae were successfully identified to GPI-1* genotype. The marked cod larvae constituted 18% of all sampled cod larvae in the first survey and 9% in the two next. The average rate of mortality was estimated to be 23% day −1 for the first 10 days after release and 12% day −1 during the next month after release. After 1 year (April 1996), the number genetically marked I-group cod in the fjord was estimated to be 〈120. The effect of the historical programme of large-scale releases of yolk-sac larvae on recruitment were evaluated and found to be small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb06103.x
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Migration patterns and recapture rates of North-east Arctic and Norwegian coastal cod reared and released under similar conditions (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 54 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A total of 5000 1-group cod of Northeast Arctic and Norwegian coastal origin were reared under similar conditions, anchor tagged and released at two sites in western Norway. There were significantly more recaptures from the coastal cod. No differences in migration patterns were detected, suggesting that mortality rates were higher in North-east Arctic cod.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00625.x
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    Paper (German National Licenses)
    Fulltext
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