An Assessment of the Level of Genetic Introgression in Irish Wild Salmon Populations from Farmed Escaped Salmon (GeneFlow)

This report presents the first nationwide assessment of genetic introgression from farmed salmon into wild Irish Atlantic salmon populations. Based on samples of over 8,000 contemporary fish (2023–2025) and historical samples (2003–2008), a SNP-based genetic approach was used to quantify farm ancestry in individual river populations. Results show evidence of introgression in approximately one third of populations sampled, with levels of geneflow considered as being generally low to moderate. Affected populations were found nationwide, including in areas distant from major aquaculture activity, although higher levels were more common near marine net-pen farms and in rivers where freshwater smolt rearing facilities are located. The findings provide a baseline for monitoring and highlight the importance of ongoing surveillance and management of salmon aquaculture installations to protect genetic integrity of wild stocks.

URI

https://hdl.handle.net/10793/2208

Description

This report evaluates gene flow from escaped farmed salmon into wild populations across Ireland, a study funded under the EMFAF Marine Biodiversity Scheme. It establishes a national genetic baseline, applies genomic tools to determine the level of genetic introgression from farmed salmon in individual river wild populations. It supports regulation, conservation planning, and international reporting obligations, and recommends continued monitoring and research.

Citation

Anon. (2026). An Assessment of the Level of Genetic Introgression in Irish Wild Salmon Populations from Farmed Escaped Salmon (GeneFlow). Marine Institute Report Series, EMFAF Operational Programme 2021–2027.