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  • 1
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Studies on genetic changes in farmed fish populations are reviewed, and the potential interactions between wild and farm escapee, and between wild and stocked, fish populations are discussed. Examples of the application of genetic markers in studies concerning survival and reproduction of stocked fish, and genetic and ecological interactions between stocks, are given for brook trout, Salvelinus fontinalis, brown trout, Salmo trutta, rainbow trout, Salmo gairdneri, cod, Gadus morhua, Guadalupe bass, Micropterus treculi, walleye, Stizostedion vitreum vitreum and chum salmon, Oncorhynchus keta. The various studies produced different results. Evidence for successful reproduction and genetic interactions between released and wild stocks have been found in a few cases. Stocked genetic material sometimes had a lower reproductive success than wild material. In one case the transplanted genetic material failed to acclimatize, and was apparently lost from the genepool in two generations. Investigations on the genetic and ecological interactions between wild and farmed populations are of great importance to the preservation of wild populations and their genetic resources.
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  • 2
    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.
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  • 3
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During the last decade, genetic studies have been carried out on samples of Atlantic herring, CIupea harengus L., from the Baltic, North Sea, British Isles, Norwegian sea-waters and in the western part of the North Atlantic Ocean. Based on direct comparisons of samples drawn from several areas, the available information on allozyme variation was compiled into a comparable data set and analysed for population structure and genetic distance. The results are discussed in relation to the present stock model for herring.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In Lake Svartavasstjønn on the Hardangervidda plateau, a fine-spotted variant of brown trout has been found. The spotted variability shows a classical Mendelian mode of inheritance. In this population genetic variability was found in LDH-5*, MDH-3* and MDH-3*. The fast allele at LDH-5* had a frequency of 0,913. This is remarkable, as this allele has been found in frequencies above 0.4 in only five out of 50 investigated populations in Norway. The genetic characteristics of brown trout from Lake Svartavasstjønn were compared with 11 other populations sampled from a broad geographical area of Norway. Among these was Lake Setningen, where fine-spotted individuals occur at low frequency. Using a cluster analysis based on eight loci found to be polymorphic in brown trout, we found no indication of a close relationship between the fine-spotted brown trout from Lake Svartavasstjønn and the population in Lake Setningen. During a field survey in 1990 we found that the reproduction of fine-spotted trout in Lake Svartavasstjønn had terminated. The fine-spotted trout represents a valuable but threatened genetic resource, and attempts are carried out to conserve it.
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  • 6
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Biochemical genetic polymorphism in cod from several fjords in Troms, northern Norway was analysed. Gene frequencies at several polymorphic loci (Hb, Pgi, Ldh, Pgm, Gpd and Idh) are given. Significant variation was found both within and between fjords, and even between samples from the same locality sampled in different years, indicating a mosaic structure of the cod population in the area studied. The results of the haemoglobin variation are compared to similar results obtained more than 20 years ago in the same and adjacent areas. The biochemical genetic variation is discussed in relation to stability of gene frequencies, isolation mechanisms and migration patterns.
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  • 7
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Releases of farmed fish, whether accidental from commercial aquaculture facilities or intentional as part of stock enhancement/ranching activities, are considered to pose a risk to native gene pools. Stock enhancement studies of Atlantic cod, Gadus morhua, based on artificially produced juveniles, were initiated in 1984 in western Norway, and genetic aspects were incorporated. In order to investigate potential interbreeding between released and wild cod, a genetically marked cod strain was developed, being homozygotic for a rare allele (GPI-1*30) expressed in white muscle tissue. In the period from 1990 to 1994, juveniles from the genetic marked strain were released in large quantities in three locations (Masfjord, Øygarden, Heimarkspollen), giving a significant increase of the marker allele in the local wild cod populations. Recently, studies have been conducted in the same areas to estimate the extent of interbreeding between the wild and released cod. The results, however, revealed no permanent increase of the frequency of the marker allele and/or GPI-1*30 heterozygotes as would be expected from interbreeding. The recent data are compared with comprehensive genetic data of the cod populations in the areas before the actual releases, covering the full period from 1994 to 2003. The present results are also discussed in relation to fishing pressure on coastal cod, migration information and reproductive success of released, genetically marked cod.
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  • 8
    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.
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  • 9
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Samples of salmon Salmo salar from the River Kachkovka and the River Nilma in northern Russia were analysed by starch gel electrophoresis and compared to three Norwegian stocks, the Neiden river in northern Norway and Øyreselv and Hopselv rivers on the west coast. The comparison included the following polymorphic loci: AAT-4*, IDDH-2*, IDHP-3*, MDH- 3,4*, MEP-2*, ESTD* as well as the newly discovered polymorphic loci FBALD-3* and TPI-3*. Samples were run side by side on gels, and the alleles found in the Russian stocks were the same as those found in the Norwegian stocks, although the electrophoretic methods used lead to differences in designations of alleles. A polymorphism in ESTD* which involves a slow allele was commonly observed in the three northern populations of the Nilma, Kachkovka and Neiden rivers. This allele was absent in the other Norwegian stocks and in a major brood stock of farmed salmon in Norway. The IDHP-3*116allele was found in unusually high frequencies in the northern populations. Thus, the variability observed at these two loci indicates a barrier to gene flow between the northern salmon stocks and the more southern stocks in the East Atlantic area.
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  • 10
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: To evaluate genetic differences in growth and survival potential as a function of light regime, cod larvae from two stocks (CC: coastal cod and AC: Arcto-Norwegian cod, spawning at latitudes of 60°N and 69°N respectively) were co-reared in mesocosms. The experiment was carried out with two artificially illuminated light regimes, corresponding to the natural photoperiod at peak spawning of the respective stocks (CC: 7–8 h distinct dark period, AC: ‘mid-night sun’ as continuous light with 2–3 h reduced light intensity). One additional regime with ambient natural light analogous to 60°N was used. At termination on day 36 post-hatch, larvae of the co-reared stocks were distinguished from each other by a genetic marker in the CC stock. Stock-specific differences in growth rate and survival were indicated, with CC larvae growing and surviving better than AC larvae. This is in agreement with earlier comparisons of larval growth in these stocks. The 69°N light regime did not enhance growth for any of the two stocks. However, natural light greatly increased growth rate of both stocks, indicat ing important mechanisms in regulation of larval feeding relative to light quality or intensity. The results may be important for choice of stock and illumination in intensive aquaculture of this species.
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