Genetic differentiation among chum salmon, Oncorhynchus keta (Walbaum), from Primorye and Sakhalin

Mitochondrial DNA (mtDNA) was examined in six wild populations of chum salmon ( Oncorhynchus keta Walbaum) distributed over the Primorye Region which extends approximately 1000 km along the Sea of Japan coast, and six populations from Sakhalin, using restriction enzyme analysis. By means of two restriction enzymes ( Bam HI and Eco 81I) eight mtDNA clonal lines were revealed in the 346 chum salmon studied. Mitochondrial DNA variants grouped the fish into two major clusters representing the Primorye and Sakhalin regions. Analysis of different chum salmon generations showed stability in the temporal population genetic structure in the three Primorye populations studied, but instability in the Sakhalin population of the Naiba River. We succeeded in detecting four major mtDNA clonal variants in Primorye chum salmon. The geographic distribution of clonal frequencies in Primorye populations has a clinal U-shape associated with the north-south axis of the Primorye region. On the whole, Sakhalin populations are less heterogeneous than Primorye ones. Two hatchery-seeded stocks from south west Sakhalin showed no mtDNA clonal variation.     

Phylogenic and geographic analysis of chum salmon Oncorhynchus keta (Walbaum) in Asian populations based on mitochondrial DNA variation

We used restriction length polymorphism (RFLP) analysis of PCR-amplified fragments of mtDNA to study the genetic structure of chum salmon populations sampled in 1993-2000 during a spawning run in five rivers: Narva (Southern Primorye), Naiba (Sakhalin Island), Sernovodnaya (Kunashir Island, Southern Kuril Islands), Ola (northwestern coast of the Sea of Okhotsk), and Anadyr' (Chukotka Peninsula). In total, 49 haplotypes were identified in 193 fish. Heterogeneity tests showed highly significant (P = 0) differences among all sample pairs. The estimated time of independent divergence of the populations or population groups is in good agreement with the time of Pleistocene glaciations. This result suggests that it is cyclic global changes during this time period that were crucial in determining the within-species divergence in chum salmon. The types of mtDNA genetic variability and mismatch distribution between haplotypes in the populations indicate that the southern regions of the Sea of Okhotsk and Sea of Japan served as refugia for chum salmon during glaciation periods.     

Microsatellite variability and differentiation of hatchery stocks of chum salmon Oncorhynchus keta Walbaum in Sakhalin

Variability at eight microsatellite loci was examined in five populations of chum salmon Oncorhynchus keta Walbaum from Sakhalin hatcheries. The population of Kalinino hatchery had the lowest heterozygosity and the lowest average number of alleles per locus. The populations examined exhibited significant differentiation, θ_ST = 0.026 on average per locus. The maximum genetic differences were found between the populations of the Kalinino and the Ado-Tymovo hatcheries; the latter differs from the remaining populations also by the highest number and high frequencies of specific alleles. The genetic features of the Taranai hatchery population, observed at microsatellite loci, reflect its “mixed” origin.     

Microsatellite variability and differentiation of hatchery stocks of chum salmon Oncorhynchus keta Walbaum in Sakhalin

Variability at eight microsatellite loci was examined in five populations of chum salmon Oncorhynchus keta Walbaum from Sakhalin hatcheries. The population of Kalinino hatchery had the lowest heterozygosity and the lowest average number of alleles per locus. The populations examined exhibited significant differentiation, theta ST = 0.026 on average per locus. The maximum genetic differences were found between the populations of the Kalinino and the Ado-Tymovo hatcheries; the latter differs from the remaining populations also by the highest number and high frequencies of specific alleles. The genetic features of the Taranai hatchery population, observed at microsatellite loci, reflect its "mixed" origin.     

The genetic structure of chum salmon (Oncorhynchus keta Walbaum) populations inferred from the nucleotide variation of the mitochondrial DNA cytochrome b gene

The nucleotide sequences of a fragment of the mitochondrial DNA cytochrome b gene were determined in 12 chum salmon populations from the Russian Far East. The level of genetic diversity in the chum salmon populations from the Iturup Island, northern coast of the Sea of Okhotsk, and Anadyr' River was found to be higher than in the populations from Kamchatka and Sakhalin, which may be related to the history of their origin and dispersal. The proportions of intrapopulation genetic variability (F(ct)) and interpopulation genetic variability within the groups (F(sc)) account for 90.87 and 0.9%, respectively, and the intergroup component (F(st)) comprises 8.23%. The predominance of one haplotype, B1, which is common for all populations studied, and a low share of intergroup variability suggest the beginning of colonization by the species of the given region from a common source (group of founders) and a relatively recent time of divergence of the chum salmon populations from the region examined.     

Mitochondrial DNA variation and genetic population structure of chum salmon Oncorhynchus keta around the Pacific Rim

A survey of mtDNA variation among populations of chum salmon Oncorhynchus keta around the Pacific Rim revealed four large population groups: Rim of the Sea of Japan, the Rim of the Okhotsk Sea and West Bering Sea, North‐west Alaska and Gulf of Alaska. The observed population structure appears to reflect isolation by distance with limited gene flow between regions and larger amounts of gene flow between populations within these four regions.     

Genetic variability and differentiation of populations of chum salmon Oncorhynchus keta (Walbaum) from the southern Russian Far East

Allozyme variation of populations of chum salmon Oncorhynchus keta from southern Russian Far East was examined. Of 55 loci screened, 31 were polymorphic. Within-population variation accounted for most of the allele diversity; FST averaged over loci was 0.052. Linkage disequilibrium was found in less than 5% of locus pairs in the chum population examined. Analysis of within- and among-population variance components of linkage disequilibrium using D-statistics (Ohta, 1982) showed that most genetic variation was distributed among populations.     

The variation in chum salmon Oncorhynchus keta (Walbaum) mitochondrial DNA and its connection with the paleogeographic events in the Northwest Pacific

The results of examining mtDNA variation in populations of chum salmon Oncorhynchus keta from the rivers of the basins of the seas of Japan and Okhotsk and in the chum salmon seasonal races of the Amur River are presented. A significant level of polymorphism between the majority of the populations studied was detected. The groups of chum salmon from the Japan and Okhotsk Seas displayed the most pronounced differences. Analysis of genetic variation demonstrated that periodic paleontologic and climatic changes in the past of this region were the most probable factor that caused the divergence of these populations. The advances and retreats of glaciers and the accompanying regressions and transgressions of the ocean level caused isolation of chum salmon in the refugia belonging hypothetically to the paleo-Suifun and paleo-Amur regions. These population groups diverged presumably 350-450 thousand years ago. Differences between the seasonal races of the Amur chum salmon are insignificant, and their emergence dates back to the period of the last Wisconsin glaciation. Probably, the main isolation factor now is the genetically determined time of spawning.     

Energy expenditures during spawning by chum salmon Oncorhynchus keta (Walbaum) in British Columbia

Physiological telemetry and proximate tissue analyses were used to assess energy expended by chum salmon Oncorhynchus keta on various behaviours during spawning in Kanaka Creek, British Columbia, Canada, and results were compared with published data on Fraser River sockeye salmon Oncorhynchus nerka , the only other species for which both types of measurements have been taken. Chum salmon arrived at the spawning grounds with body energy densities of 4·84 MJ kg⁻¹ in males and 4·62 MJ kg⁻¹ in females, lower than most sockeye salmon populations, and died with energy densities of c . 4 MJ kg⁻¹, similar to that observed in sockeye salmon and other salmonids. Moisture levels generally increased in body tissues over the spawning life, particularly in female gonads, and lipid levels decreased. Declines in protein observed over the spawning life of other Pacific salmon Oncorhynchus sp. were less evident in Kanaka Creek chum salmon. Holding behaviour constituted the dominant component of the activity schedule and energy budget of both sexes. After holding, the most expensive behaviours were nest digging in females and aggressive displays in males. Dominant males expended the most energy on behaviours each day, as indexed by oxygen consumption (3600 mgO₂ kg⁻¹), while satellite males expended nearly as much (3504 mgO₂ kg⁻¹) but females expended considerably less (2327 mgO₂ kg⁻¹). Kanaka chum salmon engaged more frequently in energetically expensive reproductive behaviours than Stuart River sockeye salmon.     

Relation between size-at-maturity and survival of progeny in chum salmon, Oncorhynchus keta (Walbaum)

Data on age- and size-at-maturity, growth, and abundance of chum salmon were collected from 1959 to 1977 at Olsen Creek in Prince William Sound, Alaska. Age composition of spawners (3 to 6-year-olds) varied from year to year: 4-year-old fish were the dominant age group in most (16 out of 19) years and 6-year-old fish usually represented less than 1 % of the returns. Mean size of older spawners was significantly larger than that of younger spawners. Size-at-maturity was similar among fish from different broods maturing at different ages in the same year. Size-at-maturity and survival of progeny were significantly related. The larger the mean size of spawners, the higher the survival rate to adulthood of their progeny. Possible reasons for this relationship are discussed.     

Introductions of distinct stocks of chum salmon, Oncorhynchus keta (Walbaum), into natural populations of the species

Populations of chum salmon, Oncorhynchus keta , are recognizable by the allelic frequencies of allozyme loci. Identification of these was used to assess the return of spawning adults to alien rivers into which they were introduced via hatchery-reared, artificially-fertilized eggs obtained from populations elsewhere in the Soviet Far East. Coefficients of return to spawn in the alien rivers were much lower than returns for the native fish, and in succeeding generations the alien fish disappeared from the spawning runs. It is concluded that transplanting salmonid eggs between populations is ineffective as a means of establishing new stock in territory already occupied by another stock, and the practice is deplored on grounds of conserving unique gene pools within species.     

大麻哈鱼卵黄囊期仔鱼异速生长及其生态学意义

运用实验生态学的方法, 对大麻哈鱼(Oncorhynchus keta Walbaum)卵黄囊期仔鱼的异速生长及器官优先发育在早期生存和环境适应上的生态学意义进行了研究。结果表明, 大麻哈鱼卵黄囊期仔鱼的感觉、摄食, 呼吸和游泳等器官快速分化, 许多关键器官均存在异速生长现象。在身体各部分中, 头部和尾部为正异速生长, 躯干部为负异速生长, 体高有先增大后减小的趋势; 在头部器官中, 眼径、口宽、吻长和眼后头长均为正异速生长; 在游泳器官中, 胸鳍、腹鳍、背鳍、臀鳍、背鳍基、臀鳍基和尾鳍均为正异速生长, 脂鳍为负异速生长, 其中, 腹鳍在全长25.31 mm、12日龄出现生长拐点, 但拐点前后均为正异速生长。大麻哈鱼卵黄囊期仔鱼感觉、摄食, 呼吸和游泳等器官的快速发育, 使出膜后的仔鱼在最短的时间内获得了与早期生存密切相关的各种能力, 对适应复杂多变的外界环境具有重要的生态学意义。       

Differentiation of chum salmon Oncorhynchus keta Walbaum populations as revealed with microsatellite and allozyme markers: a comparison

The character and extent of population differentiation in chum salmon Oncorhynchus keta from Sakhalin and Iturup were comparatively 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.     

The variability in chum salmon Oncorhynchus keta (Walbaum) mitochondrial DNA and its connection with the paleogeological events in the northwest Pacific

The results of examining mtDNA variability in populations of chum salmon Oncorhynchus keta from the rivers of the basins of the seas of Japan and Okhotsk and in the chum salmon seasonal races of the Amur River are presented. A significant level of polymorphism between the majority of the populations studied was detected. The groups of chum salmon from the seas of Japan and Okhotsk displayed the most pronounced differences. Analysis of genetic variability demonstrated that periodic paleontologic and climatic changes in the past of this region were the most probable factor that caused the divergence of these populations. The advances and retreats of glaciers and the accompanying regressions and transgressions of the ocean level caused isolation of chum salmon in the refugia belonging hypothetically to the paleo-Shuifen and paleo-Amur regions. These population groups diverged presumably 350–450 thousand years ago. Differences between the seasonal races of the Amur chum salmon are insignificant, and their emergence dates back to the period of the last Wisconsinian glaciation. Probably, the main isolation factor now is the genetically determined time of spawning.     

The parasitic fauna of the Anadyr chum salmon (Oncorhynchys keta Walbaum)

Data on a parasite fauna of the chum salmon from the Anadyr' River basin are given. 9 parasite species have been found including 3 species of medical importance.     

Identification of the sex chromosome pair in chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha)

Fluorescence in situ hybridization (FISH) using a probe to the male-specific GH-Y (growth hormone pseudogene) was used to identify the Y chromosome in the karyotypes of chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha). The sex chromosome pair is a small acrocentric chromosome pair in chum salmon and the smallest metacentric chromosome pair in pink salmon. Both of these chromosome pairs are morphologically different from the sex chromosome pairs in chinook salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch). The 5S rRNA genes are on multiple chromosome pairs including the sex chromosome pair in chum salmon, but at the centromeres of two autosomal metacentric pairs in pink salmon. The sex chromosome pairs and the chromosomal locations of the 5S rDNA appear to be different in all five of the North American Pacific salmon species and rainbow trout. The implications of these results for evolution of sex chromosomes in salmonids are discussed.     

Extension of a set of microsatellite markers for more precise identification of chum salmon (Oncorhynchus keta Walbaum)

A set often microsatellite loci enabling fairly accurate identification of the chum salmon individuals from geographically distant groups was designed at the Laboratory of Genetic Identification, Vavilov Institute of General Genetics, Russian Academy of Sciences. However, identification of the individuals from closely located basins performed using these loci was not sufficiently precise. The present study was focused on the improvement of the resolution of the method through increasing the number microsatellite loci used. In this study, typing of additional microsatellite loci of chum salmon and evaluation of the change of the degree of identification with the increase of the number ofmicrosatellite loci used is described. It was shown that the identification accuracy permanently increased with the increase of the number of microsatellite markers used.     

Microsatellite DNA variation in sockeye salmon Oncorhynchus nerka (Walbaum, 1792) populations of eastern Kamchatka

The allelic variations of eight microsatellite loci (Ots107, Oki1a, Oki1b, One104, One109, OtsG68, OtsG85, and Oki6) were examined in sockeye salmon Oncorhynchus nerka (Walbaum) populations of eastern Kamchatka. Samples from river basins of the Karaginskiy and Olyutorskiy districts in the northern part of the investigated region are characterized by a smaller number of allelic variants and lower heterozygosity, compared to samples from the Kamchatka River basin. A fit to the Hardy-Weinberg distribution was found at most of the loci that were studied in all samples. The average differentiation between populations (st) over the eight loci was 2.93%, which corresponds to the statistical significance level. The most highly polymorphic loci proved to be the least differentiating between the analyzed samples.