Genetic Population Dynamics of Atlantic Salmon

The genetic population dynamics of Atlantic salmon encompass patterns of diversity, structure and adaptive change that arise from both natural and anthropogenic influences across the species’ North Atlantic range. As an anadromous species, Atlantic salmon undertake complex migrations between freshwater nurseries and marine feeding grounds, creating opportunities for gene flow as well as local adaptation. Genomic approaches, particularly the use of single nucleotide polymorphisms (SNPs) and whole-genome resequencing, have revealed fine-scale population structure, demographic declines and signatures of selection linked to temperature, migration timing and disease resistance. Effective population size estimates indicate widespread historical and recent reductions, with consequences for adaptive potential. Mixed-stock and genetic stock identification methods have improved the resolution of stock composition in mixed fisheries, informing sustainable management. Simultaneously, studies of domesticated and hatchery-derived strains have highlighted potential genetic introgression with wild populations and the polygenic basis of traits such as growth and maturation. Understanding these dynamics is critical for conservation, climate resilience and aquaculture practices, ensuring both the persistence of wild stocks and the sustainability of fisheries and breeding programmes.

Research from Nature Portfolio

Recent studies have reconstructed changes in effective population size (Ne) for Atlantic salmon across the North Atlantic, revealing that more than 60 percent of populations have undergone significant declines in recent decades. Temperature-associated trends were identified as a key driver of reduced Ne, while genome-wide scans uncovered polygenic associations with demographic decline. Regions involved in metabolic, developmental and physiological pathways exhibited altered diversity in declining populations, consistent with observed shifts in body size and phenology. These findings emphasise the power of genomic resources to link genotype with fitness and to forecast vulnerability under ongoing environmental change.

Genetic Population Dynamics of Atlantic Salmon publication trend

The graph below shows the total number of articles in genetic population dynamics of atlantic salmon across all publications each year (not limited to Nature Index journals).

Technical terms

Anadromous migration: Seasonal movement of salmon from freshwater to marine environments and back, affecting gene flow and population structure.

Effective population size (Ne): The number of individuals in an idealised population that would show the same level of genetic drift as the observed group.

Single nucleotide polymorphism (SNP): A single-base variation in the genome widely used as a genetic marker for diversity and population studies.

Mixed-stock analysis: Genetic method to estimate proportional contributions of multiple source populations in mixed fisheries or aggregations.

Genetic stock identification (GSI): Assignment of individuals to their population of origin based on allele frequency differences among stocks.

Selective sweep: Reduction of genetic diversity surrounding a beneficial allele that has rapidly increased in frequency due to selection.

Polygenic adaptation: Adaptive change involving small allele‐frequency shifts at many loci rather than a single major‐effect gene.

References

1. Genomic signatures and correlates of widespread population declines in salmon. Nature Communications (2019).
2. Integrating genetic analysis of mixed populations with a spatially explicit population dynamics model. Methods in Ecology and Evolution (2018).
3. Genotyping‐by‐sequencing of genome‐wide microsatellite loci reveals fine‐scale harvest composition in a coastal Atlantic salmon fishery. Evolutionary Applications (2018).
4. Applications of random forest feature selection for fine‐scale genetic population assignment. Evolutionary Applications (2017).