Interregional differentiation of chum salmon from Sakhalin and South Kurils inferred from microsatellite markers

Russian Journal of Genetics (Impact Factor: 0.45). 06/2008; 44(7):833-840. DOI: 10.1134/S1022795408070119


Variability at ten microsatellite loci was examined in wild and hatchery populations of chum salmon (Oncorhynchus keta Walbaum) from the Sakhalin Island and Southern Kuril Islands, Iturup and Kunashir. Substantial genetic differences between
Sakhalin and South Kurils chum salmon (the differentiation reached 6.0%) were revealed. Statistically significant differences
between chum salmon from Iturup and those from Kunashir were demonstrated, as well as between the chum salmon populations
from different rivers within the islands. It was shown that in different types of population comparisons, different marker
sets were most informative.

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    • "Using the primers for Oki1, we obtained two distinct zones on a gel that can be interpreted as a result of duplication followed by evolutionary molecular divergence into two microsatellite loci with identical flanking regions; both loci were used in this study with notation Oki1-1 (180– 270 b.p.) and Oki1-2 (90–110 bp). The procedures for DNA extraction, amplification, fragment analysis, and standard statistics of microsatellite variation at the loci used have been described elsewhere (Afanasiev et al. 2008). "
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    ABSTRACT: A harvested stock of chum salmon homing to Kurilskiy Bay, Iturup Island, consists of two genetically distinct river populations that reproduce in two rivers that drain into the bay and are characterized by limited gene flow. One of these is small and can be regarded as wild, whereas the other is much larger and, until recently, was composed of naturally reproducing components spawning in the river’s mainstem and tributaries, with almost no hatchery reproduction during the past two decades. The only human impact on reproduction of the chum salmon stock was regulation of the escapement, with officially accepted limits to avoid ‘over-escapement’. Recently the hatchery began to release a large amount of chum salmon juveniles. As confirmed by data on variation in both age composition and microsatellite DNA, first-generation hatchery-origin fish that returned from the first large releases occupied spawning grounds and presumably competed directly with, and potentially displaced wild fish. The most dramatic example is a genetically distinct beach-spawning form of chum salmon that was swamped by much more numerous hatchery-origin fish of the river-spawning form. In order to restore and support naturally reproduced population components, careful estimation of the carrying capacity of natural spawning grounds is necessary with efforts to increase escapement to these habitats. We also recommend concerted efforts to restore and conserve a unique beach-spawning population of chum salmon. We further recommend development of a marking program for direct estimation of straying and evaluation of ecological and genetic impacts of hatchery fish on neighboring wild and natural populations. KeywordsChum salmon–Hatchery population expansion–Microsatellite DNA marker–Age composition–Release-return dynamics–Wild-hatchery fish
    Environmental Biology of Fishes 05/2011; 94(1):249-258. DOI:10.1007/s10641-011-9873-4 · 1.57 Impact Factor
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    ABSTRACT: The features and extent of population differentiation in chum salmon Oncorhynchus keta from Sakhalin and Iturup Islands were studied with 10 microsatellite and 12 allozyme markers. It was demonstrated with the example of allozyme polymorphism at the EstD locus that the effect of an individual locus with one major allele is capable of distorting the total picture of population differentiation. Multiallelic microsatellites were more efficient in revealing the genetic structure of chum salmon populations at the levels of differences between regional populations and between the stocks of individual rivers of the same region.
    Russian Journal of Genetics 06/2008; 44(7):841-848. DOI:10.1134/S1022795408070120 · 0.45 Impact Factor
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    ABSTRACT: Population studies with the use of microsatellite markers face a problem of null alleles, i.e., the absence of a PCR product, caused by the mutations in the microsatellite flanking regions, which serve as the sites of primer hybridization. In this case, the microsatellite primer associated with such mutation is not amplified, leading to false homozygosity in heterozygous individuals. This, in turn, results in biased population genetic estimates, including the excess of homozygotes at microsatellite loci. Analysis of the population structure of a Pacific salmon species, chum salmon (Oncorhynchus keta Walbaum), revealed the presence of null alleles at the Oke3 microsatellite locus in the population samples, in which an excess of homozygotes was observed. The analysis was performed using different combinations of modified primers chosen to match the Oke3 locus. The use of these primers enabled identification of true heterozygotes among those individuals, which were previously diagnosed as homozygotes with the use of standard primers. Removal of null alleles eliminated the excess homozygotes in the chum salmon samples described. In addition to the exclusion of false homozygosity, the use of modified primers makes it possible to introduce polymorphic primer variants associated with certain microsatellite alleles into population studies.
    Russian Journal of Genetics 08/2010; 46(8):1019-1022. DOI:10.1134/S1022795410080168 · 0.45 Impact Factor
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