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Genome Overview
Genome size: ~2.97 Gb (gigabases)
Chromosomes: 29 pairs (2n = 58) European
Chromosomes: 27 pairs (2n=54) North American
Whole-genome duplication: Salmonids underwent a 4R genome duplication event (~80–100 MYA), giving them duplicated gene sets. This contributes to their genetic complexity and adaptability.
The Salmo salar genome was fully sequenced in 2016.
Salmo salar life cycle illustrated, Atlantic salmon life cycle - Emily S. Damstra
Evolutionary History
The evolutionary journey of the Atlantic salmon (Salmo salar) has been shaped by powerful natural and environmental forces, as well as cooperative genetic and behavioral processes that have enabled it to thrive in both freshwater and marine ecosystems. Natural selection plays a central role in this process, favoring individuals whose traits enhance survival during the demanding life cycle salmon undergo—especially their migration between rivers and the ocean.
Traits such as smoltification timing, salt tolerance, body shape, and stamina are strongly selected for, ensuring that only individuals well-suited to these transitions successfully reproduce. there is still a small amount of gene flow between populations, often from “straying” individuals who spawn in non-natal rivers.
Occasional mixing helps maintain genetic diversity across the species’ range and can introduce beneficial genetic variation into new or recovering habitats.
Exhibit remarkable phenotypic plasticity, meaning they can modify their physiology or behavior in response to environmental conditions. For example, the timing of smoltification, migration, and even age at maturity can shift depending on temperature, daylight, and food availability. This plasticity allows salmon to cope with short-term changes and buffers populations against rapid environmental disruption, while also enabling long-term evolutionary adaptation
Human Co Evolution Positives
Governments and NGOs have created protected rivers, enforced fishing regulations, and established spawning sanctuaries.
Cryopreservation of salmon sperm and egg banking have also been used to preserve genetic lines of endangered populations. Preserving and protecting salmon in general is important as salmon are known to bring marine nutrients upstream into freshwater and forest ecosystems, benefiting plants, invertebrates, birds, and mammals. They play a role in nutrient cycling and food web support.
Human Co Evolution Negatives
Introduction of strong, rapid evolutionary pressures.
Overfishing has led to earlier age at maturity and smaller average body size in response to being heavily fished.
Traits such as faster growth rates, with bolder behavior, reduced homing precision, and reduced predator avoidance all contribute to a decline in the overall population as a result of hatchery programs.
Human built structures like dams, culverts, and channelization have altered river flow and temperature forcing salmon populations to evolve shorter migration distances or adopt a non migratory life cycle.
Atlantic Salmon from Hatcheries (protected environments) show a decrease and size with brighter colors and more spots making them easily distinguishable and prone to attacks from predators due to less camouflage in the environment. Spot patterns of Atlantic salmon primarily vary with environment, and... | Download Scientific Diagram
Fillet Coloration: As mentioned, variation in the bco1 gene on chromosome 26 contributes to differences in flesh pigmentation, ranging from pale to deep orange/red.
Environmental impacts of Salmon farming, Environmental Impacts - Best Fishes
Examples of Salmo salar Farming
Europe begins largest land-based salmon farming facility
Washington state Aquaculture farm (Aquaculture)
Aquaculture
Salmon are caught with a net and moved to a farming facility.
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