Population Genetics of Pacific Salmon Paper

Population Genetics of Pacific Salmon Paper
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The different ways that salmon hatcheries affect the genetic structure of wild populations and why these changes threaten the long term sustainability of salmon fisheries
Unlike the fish in hatcheries, the wild salmon populations (sockeye, coho, pink, chum, and Chinook) have highly specialized adaptations to the natural environment, and this improves their ability to cope with environmental changes. For instance, they can cope better with increased ocean temperatures and extreme variations of the currents and they are used to the environment. The release of billions of salmon fish species in the wild especially by the U.S. Canada and Japan has increased demand for salmon and boost production at hatcheries. However, this creates problems because the hatchery salmon affect the long-term survival of wild salmon. The hatchery- reared salmons affect the genetics of the wild population in various ways such as drift, interbreeding, admixture and adaptation.
In a study by Kovach, Gharrett & Tallmon (2012), the researchers found out that there are genetic changes in the population of pink salmon when they looked at phenological shifts associated with earlier migration timing based on data from 1979 to 2011. There was a decrease in late-migrating pink salmon population mainly in odd years and the case of microevolutionary changes influencing early migration timing in other salmonid species in the even-year population (Kovach, Gharrett & Tallmon, 2012). Just as there were changes in the species as they adapted to climate change, as the population of hatchery fish increase in the wild, there may be selection against the wild species similar to selection against the late migrating species.
The hatched salmon that are released to the ocean outnumber the wild Pacific salmon over time, and when there is breeding and inbreeding there are reduced genetic differences in the salmon population. However, it is not only the genetic admixing with native populations that affect the Pacific salmon species since when there is high density and robust wild populations it is less likely that fish from the salmon hatcheries will manage to reproduce effectively. Epigenetic modifications in hatchery salmons is more common because of artificial selection, but this also makes the Pacific salmon less fit for the wild compared to the naturally spawning populations (Le Luyer et al., 2017). In many cases, in the hatch...