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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Offspring from seven family groups of Arcto-Norwegian cod (AN) and a genetically marked Norwegian coastal cod (NC) broodstock, were mixed at metamorphosis and raised in the same rearing unit. The fish were transferred subsequently to a net-pen and held under standard farming conditions. In December 1992, 466 cod juveniles were measured, weighed, and tagged individually. Length and weight changes were monitored until the fish matured (January 1994). Genotyping of each individual was performed using enzyme electrophoresis to identify the fish to strain. Prespawning females were examined for organ weights and stage of maturity. There were population specific Differences in growth performance. NC displayed significantly higher specific growth rate (SGR) and daily length increment (DLI) during spring/summer season. The AN had significantly lower hepatosomatic and gonadosomatic indices, and were thinner than the NC, indicating Differences in body form and energy allocation pattern between the two strains. All NC (both sexes) became sexually mature at the age of 2 years while 2% of fish in the AN group were still immature at the end of the experiment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 21 (1990), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 23 (1992), S. 0 
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 21 (1990), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The behaviour was compared of juvenile reared and wild cod, Gadus morhua L., towards a potential predator. The cod were allowed to swim and feed freely in a tank, separated from a predator (large cod) by a transparent Plexiglas wall. The reared cod remained further from the predator than the wild cod, and were slower to approach the predator. The relevance of these findings for extensive rearing of cod is discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 52 (1998), S. 0 
    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
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 51 (1997), S. 0 
    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
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Less than 2% of the O–group cod Gadus morhua of mean length 8 cm at release survived their first 3 months in the sea, while c. 75% of those of mean length 12 cm survived a similar period. There was no difference in mortality rates during their first winter at sea between groups with mean lengths 12 and 17 cm at release. The results could probably be explained by the relatively small sizes of predatory fishes in the fjord and the degree of overlap between size at release and the preferred prey sizes of the predators.
    Type of Medium: Electronic Resource
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  • 9
    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
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