Farm salmon escape event: levels of farm/wild hybridisation

Results of a genetic survey to examine levels of farm/wild hybrid salmon in rivers local to a large-scale farm escape in in south west Scotland and north east England. This occurred in 2020 when MOWI’s Carradale North fish farm shifted position after its seabed anchors became dislodged during Storm Ellen.


Samples and genotyping

In total, 118 sites were fished as part of the survey, with 2,390 and 2,932 samples collected in 2020 and 2021 respectively (Figure 1, Table 1, Appendix 1). An overall genotyping success rate of 99.2% resulted in 5,281 samples available for analysis.

Figure 1 Map showing location of the escape event and the sampled sites in Scotland and England. Generalised Random Tessellation Stratified ( GRTS) regions are identified (Argyll, Ayrshire, Carradale, Clyde) together with GRTS and ad-hoc sites within these regions. Additional ad-hoc sites on the Scottish river Bladnoch, and English rivers Eden, Derwent and Ehen also shown.
Table 1: Summary of sites surveyed, samples genotyped and genotyping success. Full breakdown in Appendix 1.
Origin Sites Samples genotyped Samples after QC Genotyping success (%)
2020 90 2390 2358 98.7
2021 98 2594 2586 99.7
2021 10 338 337 99.7
Totals 198 5322 5281 99.2



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