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Research article - Peer-reviewed, 2021

A century of genetic homogenization in Baltic salmon-evidence from archival DNA

Ostergren, Johan; Palm, Stefan; Gilbey, John; Spong, Goran; Dannewitz, Johan; Konigsson, Helena; Persson, John; Vasemagi, Anti

Abstract

Intra-species genetic homogenization arising from anthropogenic impacts is a major threat to biodiversity. However, few taxa have sufficient historical material to systematically quantify long-term genetic changes. Using archival DNA collected over approximately 100 years, we assessed spatio-temporal genetic change in Atlantic salmon populations across the Baltic Sea, an area heavily impacted by hydropower exploitation and associated with large-scale mitigation stocking. Analysis was carried out by screening 82 SNPs in 1680 individuals from 13 Swedish rivers. We found an overall decrease in genetic divergence and diminished isolation by distance among populations, strongly indicating genetic homogenization over the past century. We further observed an increase in genetic diversity within populations consistent with increased gene flow. The temporal genetic change was lower in larger wild populations than in smaller wild and hatchery-reared ones, indicating that larger populations have been able to support a high number of native spawners in relation to immigrants. Our results demonstrate that stocking practices of salmon in the Baltic Sea have led to the homogenization of populations over the last century, potentially compromising their ability to adapt to environmental change. Stocking of reared fish is common worldwide, and our study is a cautionary example of the potentially long-term negative effects of such activities.

Keywords

Salmo salar; historical DNA; human-induced; genetic change; conservation

Published in

Proceedings of the Royal Society B: Biological Sciences
2021, volume: 288, number: 1949, article number: 20203147
Publisher: ROYAL SOC

Authors' information

Swedish University of Agricultural Sciences, Department of Aquatic Resources
Swedish University of Agricultural Sciences, Department of Aquatic Resources
Gilbey, John
Freshwater Fisheries Lab
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies
Swedish University of Agricultural Sciences, Department of Aquatic Resources
Swedish University of Agricultural Sciences, Department of Wildlife, Fish and Environmental Studies
Swedish University of Agricultural Sciences, Department of Aquatic Resources
Swedish University of Agricultural Sciences, Department of Aquatic Resources
Estonian University of Life Sciences

Sustainable Development Goals

SDG14 Life below water

UKÄ Subject classification

Genetics
Zoology

Publication Identifiers

DOI: https://doi.org/10.1098/rspb.2020.3147

URI (permanent link to this page)

https://res.slu.se/id/publ/111937