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Salmonids are an important cultural and ecological resource exhibiting near worldwide distribution between their native and introduced range. Previous research has generated linkage maps and genomic resources for several species as well as genome assemblies for two species. We first leveraged improvements in mapping and genotyping methods to create a dense linkage map for Chinook salmon Oncorhynchus tshawytscha by assembling family data from different sources. We successfully mapped 14 620 SNP loci including 2336 paralogs in subtelomeric regions. This improved map was then used as a foundation to integrate genomic resources for gene annotation and population genomic analyses. We anchored a total of 286 scaffolds from the Atlantic salmon genome to the linkage map to provide a framework for the placement 11 728 Chinook salmon ESTs. Previously identified thermotolerance QTL were found to colocalize with several candidate genes including HSP70, a gene known to be involved in thermal response, as well as its inhibitor. Multiple regions of the genome with elevated divergence between populations were also identified, and annotation of ESTs in these regions identified candidate genes for fitness related traits such as stress response, growth and behaviour. Collectively, these results demonstrate the utility of combining genomic resources with linkage maps to enhance evolutionary inferences. [ABSTRACT FROM AUTHOR]

Gene sequence similarity due to shared ancestry after a duplication event, that is paralogy, complicates the assessment of genetic variation, as sequences originating from paralogs can be difficult to distinguish. These confounded sequences are often removed prior to further analyses, leaving the underlying loci uncharacterized. Salmonids have only partially rediploidized subsequent to a whole-genome duplication; residual tetrasomic inheritance has been observed in males. We present a maximum-likelihood-based method to resolve confounded paralogous loci by observing the segregation of alleles in gynogenetic haploid offspring and demonstrate its effectiveness by constructing two linkage maps for chum salmon (Oncorhynchus keta), with and without these newly resolved loci. We find that the resolved paralogous loci are not randomly distributed across the genome. A majority are clustered in expanded subtelomeric regions of 14 linkage groups, suggesting a significant fraction of the chum salmon genome may be missed by the exclusion of paralogous loci. Transposable elements have been proposed as drivers of genome evolution and, in salmonids, may have an important role in the rediploidization process by driving differentiation between homeologous chromosomes. Consistent with that hypothesis, we find a reduced fraction of transposable element annotations among paralogous loci, and these loci predominately occur in the genomic regions that lag in the rediploidization process. [ABSTRACT FROM AUTHOR]

The emerging field of next-generation sequencing (NGs) is rapidly expanding capabilities for cutting edge genomic research, with applications that can help meet marine conservation challenges of food security, biodiversity loss, and climate change. Navigating the use of these tools, however, is complex at best. Furthermore, applications of marine genomic questions are limited in developing nations where both marine biodiversity and threats to marine biodiversity are most concentrated. his is particularly true in southeast Asia. The first Pan-Pacific Advanced studies Institute (PacAsI) entitled "Genomic Applications to Marine science and resource Management in southeast Asia" was held in July 2012 in Dumaguete, Philippines, with the intent to draw together leading scientists from both sides of the Pacific Ocean to understand the potential of NGs in helping address the aforementioned challenges. Here we synthesize discussions held during the PacAsI to provide perspectives and guidance to help scientists new to NGs choose among the variety of available advanced genomic methodologies specifically for marine science questions. [ABSTRACT FROM AUTHOR]

Numerous empirical studies have reported lack of migration-drift equilibrium in wild populations. Determining the causes of nonequilibrium population structure is challenging because different evolutionary processes acting at a variety of spatiotemporal scales can produce similar patterns. Studies of contemporary populations in northern latitudes suggest that nonequilibrium population structure is probably caused by recent colonization of the region after the last Pleistocene ice age ended ~13 000 years ago. The chum salmon's ( Oncorhynchus keta) range was fragmented by dramatic environmental changes during the Pleistocene. We investigated the population structure of chum salmon on the North Alaska Peninsula ( NAP) and, using both empirical data and simulations, evaluated the effects of colonization timing and founder population heterogeneity on patterns of genetic differentiation. We screened 161 single nucleotide polymorphisms and found evidence of nonequilibrium population structure when the slope of the isolation-by-distance relationship was examined at incremental spatial scales. In addition, simulations suggested that this pattern closely matched models of recent colonization of the NAP by secondary contact. Our results agree with geological and archaeological data indicating that the NAP was a dynamic landscape that may have been more recently colonized than during the last deglaciation because of dramatic changes in coastal hydrology over the last several thousand years. [ABSTRACT FROM AUTHOR]

Until recently, single nucleotide polymorphism (SNP) discovery in nonmodel organisms faced many challenges, often depending upon a targeted-gene approach and Sanger sequencing of many individuals. The advent of next-generation sequencing technologies has dramatically improved discovery, but validating and testing SNPs for use in population studies remain labour intensive. Here, we detail a SNP discovery and validation pipeline that incorporates 454 pyrosequencing, high-resolution melt analysis (HRMA) and 5′ nuclease genotyping. We generated 4.59 × 10 bp of redundant sequence from transcriptomes of two individual chum salmon, a highly valued species across the Pacific Rim. Nearly 26 000 putative SNPs were identified-some as heterozygotes and some as homozygous for different nucleotides in the two individuals. For validation, we selected 202 templates containing single putative SNPs and conducted HRMA on 10 individuals from each of 19 populations from across the species range. Finally, 5′ nuclease genotyping validated 37 SNPs that conformed to Hardy-Weinberg equilibrium expectations. Putative SNPs expressed as heterozygotes in an ascertainment individual had more than twice the validation rate of those homozygous for different alleles in the two fish, suggesting that many of the latter may have been paralogous sequence variants. Overall, this validation rate of 37/202 suggests that we have found more than 4500 templates containing SNPs for use in this population set. We anticipate using this pipeline to significantly expand the number of SNPs available for the studies of population structure and mixture analyses as well as for the studies of adaptive genetic variation in nonmodel organisms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article focuses on the 20th Wakefield Symposium, "The Genetics of Subpolar Fish and Invertebrates," which is the successor of the 11th Wakefield Symposium. One of the predominant themes of both symposia was the descriptive study of population structure. Descriptive studies are an important step in developing management or conservation plans because they can provide markers for use in stock identification programs and because they can identify distinct productivity units in species that do not have convenient or obvious geographical boundaries, such as many marine species.

Genetic marking, the manipulation of allelic frequencies to tag fish stocks, was applied to chum salmon Oncorhynchus keta released in Kennedy Creek, a tributary to Totten Inlet in south Puget Sound, Washington. Our objectives were to conduct a Petersen mark-recapture population census of smolts residing in Totten Inlet and to identify the contribution of marked fish to subsequent spawning runs. Male spawners were selected for expression of the 115 allele of aspartate aminotransferase Aat 1,2 or the 90 allele of 6-phosphogluconate dehydrogenase Pgdh. The respective frequencies were thus increased from about 0.12 and 0.01 among the native fish to about 0.25 and 0.11 among the progeny of selected males. Eggs were incubated in streamside gravel box incubators and 11 x 106 hatched fish were released to Kennedy Creek during 1978-1980. Fish from the genetically marked broods made up 15-51% of the chum salmon smolts resident in Totten Inlet each spring, 1978-1980, and Petersen mark-recapture population estimates indicated that the total population size ranged from 2.2 x 106 to 4.3 x 106. In 1979-1981, 6-29% of adults returning to Kennedy Creek to spawn were fish from marked broods. This study validated the use of genetic marking as a tool for use in fisheries research and management. [ABSTRACT FROM AUTHOR]

Previous studies demonstrated reduced survivorship of pink salmon embryos from populations in Prince William Sound, Alaska, USA, that were exposed to Exxon Valdez-released oil compared with populations frommatched nonoiled streams. Survivorship was also significantly decreased in embyros from lineages that were oiled in Prince William Sound and reared in clean water under controlled hatchery conditions compared with the descendants of nonoiled lineages. This suggests that the effect of oiling on pink salmon populations was persistent and could be transmitted intergenerationally. However, the ability of environmentally released oil to cause DNA sequence alterations in natural populations has yet to be demonstrated. We used polymerase chain reactionanalysis to screen for alterations in the K-ras oncogene in DNA frompink salmon embryos that were exposed under controlled laboratory conditions to weathered Prudhoe Bay crude oil. Polymerase chain reaction and direct DNA sequence analyses were used to identify mutational hotspots within exons 1 and 2 of K-ras, and 3 primer mismatch analysiswas used to determine the frequency of mutations in the 40 offspringof two families of pink salmon that were experimentally exposed to oiled or clean gravel. Mutations were only observed at codons 12, 13, and 61 of K-ras, sites that are frequently mutated in animal and human tumors. All mutations resulted in deduced amino acid substitutions.As expected, in all individuals exhibiting mutations, the copy number of the normal allele exceeded that of the mutated allele. The frequencies of mutations in oiled embryos at K-ras exons 1 and 2 were 68 and 41%, respectively. K-ras mutations were not observed in siblings that were exposed to clean gravel or in the parents of the two experimental matings. These results indicate that exposure of pink salmon embryos to weathered Prudhoe Bay crude oil under controlled laboratory conditions can elicit somatic cell mutations in high frequency at mutationa [ABSTRACT FROM AUTHOR]

The variability of 45 single nucleotide polymorphism loci (SNP) was studied in sockeye salmon from the Kamchatka River basin and four lake-river systems of the west coast of the Bering Sea. Based on the genetic differentiation estimates for the largest sockeye salmon populations of Eastern Kamchatka and Chukotka, the examined samples were combined into two regional groups represented by the population of the Kamchatka River drainage, which included numerous local subpopulations and seasonal races, and the northern population grouping from the rivers of Olutorsko-Navarinsky raion, wherein the sockeye salmon from Maynypilginskaya Lake-River system was relatively isolated. Considerable divergence was observed between the island (Sarannoe Lake, Bering Island) and continental populations. Genetic heterogeneity was revealed and groups of early- and late-maturing individuals were isolated in the sample of late-run sockeye salmon from Kamchatka River. In Apuka River, subdivision of the spawning run into two genetically distinct spatial and temporal groupings was also observed. The results suggest that the differentiation of sockeye salmon samples by single nucleotide substitution frequencies was largely due to differences in the direction and strength of local selection at some loci in the population complexes and intrapopulation groupings from the examined river basins of Eastern Kamchatka, Chukotka, and Commander Islands.

The variability of 45 single nucleotide polymorphism (SNP) loci was studied in nine samples of the sockeye salmon Oncorhynchus nerka from the rivers of southwestern Kamchatka. The Wahlund effect, gametic disequilibrium at some loci, and a decrease in interpopulation genetic diversity estimates observed in samples from the Bolshaya River outlet are explained in terms of the samples' heterogeneity. Partitioning of mixed samples using some biological characteristics of the individuals led to a noticeable decrease in the frequency of these phenomena. It was demonstrated that the allelic diversity between the populations within the river Plotnikovs accounted for the larger part of genetic variation, as compared to the differentiation between the basins. The SNP loci responsible for intra- and interpopulation differentiation of sockeye salmon from the rivers of southwestern Kamchatka were identified. Some recommendations for field population genetic studies of Asian sockeye salmon were formulated.

We describe the inheritance of 460 PCR-based loci in the polyploid-derived pink salmon (Oncorhynchus gorbuscha) genome using gynogenetic haploid embryos. We detected a length polymorphism in a growth hormone gene (GH-2) intron that is caused by an 81 bp insertion homologous to the 3' end of the salmonid short interspersed repetitive element (SINE) SmaI. Such insertion polymorphisms within species bring into question the use of SINEs as phylogenetic markers. We confirmed that a microsatellite locus encodes a PCR-null allele that is responsible for an apparent deficit of heterozygotes in a population sample from Prince William Sound. Another set of microsatellite primers amplified alleles of the same molecular weight from both loci of a duplicated pair. In our analysis of several PCR-based multilocus techniques, we failed to detect evidence of comigrating fragments produced by duplicated loci. Segregation analysis of PCR-based markers using gynogenetic haploid embryos ensures that the interpretation of molecular variation is not complicated by heterozygosity, diploidy, or gene duplication. We urge investigators to test the inheritance of polymorphisms in salmonids prior to using them to measure genetic variation.