Study on fish interbreeding is published

A major report has been published on the extent of interbreeding between wild Atlantic salmon and fish farm escapees in Irish rivers.

The study was led by University College Cork and undertaken in collaboration with Inland Fisheries Ireland (IFI) and Teagasc. For the analysis, IFI collected samples of salmon in rivers from 133 locations across Ireland between 2023 and 2025. Samples collected between 2003 and 2008 from 61 rivers were also used in the study.

The study has found evidence of farmed salmon genes in approximately one third of the wild salmon populations sampled. The analysis noted elevated levels of farmed genes in wild stocks sampled near marine salmon farms, and near freshwater salmon farms.

In addition, wild salmon populations that were distant from major areas of salmon farming were also found to be affected

IFI is the State agency responsible for conserving, protecting and managing fish, including wild Atlantic salmon populations, in Ireland.

Commenting on the report findings, Dr Michael Millane, Senior Research Officer at IFI said: “Escaped farmed salmon pose a risk to the continued sustainability of our wild Atlantic salmon, which are already vulnerable to a wide range of other pressures.

“When farmed salmon interbreed with our wild salmon, they dilute the unique genetic integrity that adapts wild populations to their river of origin.

This genetic disruption can ultimately lower off-spring survival rates and reduce the overall resilience of wild populations to other pressures that impact them."

Dr Fiona Kelly, Head of Research, Policy and Risk at IFI said the report findings provide a valuable baseline for future such assessments and will guide further research into the implications for wild Atlantic salmon populations.

She added: “The project has received a funding extension and will collect samples during summer 2026 to provide further insights into interbreeding of fish farm escapes. The findings are also useful to better inform the regulation of the salmon farming sector in Ireland.”

IFI said it is committed to providing evidence-based research that informs policy to support the sustainable management, conservation and restoration of fish and their ecosystems in Ireland.

This report was funded through the EMFAF Marine Biodiversity Programme 2021-2027, co-funded by the EU and the Marine Institute on behalf of the Government of Ireland. It is the first such study to comprehensively examine this topic in Ireland.