A national assessment of the influence of farmed salmon escapes on the genetic integrity of wild Scottish Atlantic salmon populations

• Main Author: Gilbey, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Marine Scotland Science 1900
• Subjects: Fish; Fisheries and aquaculture; Human activities; Atlantic salmon
• Online Access: https://dx.doi.org/10.7489/12386-1; https://data.marine.gov.scot/dataset/national-assessment-influence-farmed-salmon-escapes-genetic-integrity-wild-scottish-atlantic

Interbreeding between escaped farmed Atlantic salmon and wild indigenous salmon (hybridisation) introduces genetic material from farmed stocks into wild populations (introgression) with resulting disruption of the adaptive genetic composition of individuals and populations. This can impact their fitness resulting in a significant negative pressure on the viability of wild populations. Recent advances in analytical and statistical techniques are able to differentiate between farmed salmon of Norwegian origin, native wild Scottish salmon and progeny resulting from interbreeding. By sampling a number of juvenile salmon from a particular location it also possible to estimate the proportion of foreign genetic material present in wild Scottish salmon populations and to identify whether this is due to recent or historical events. Monitoring the proportions of wild fish affected by hybridisation is routinely carried out in other countries, and can feed into management decision making. This is the first time a survey to examine the genetic status of populations has been conducted across the geographical extent of Scotland. : A bespoke panel of genetic markers, developed specifically to detect genetic changes in Scottish wild salmon, was used to screen tissue samples collected from juvenile fish from 252 sites across Scotland between 2018 and 2019 (n = 2,964 fish). These fish were sampled as part of the National Electrofishing Programme for Scotland (NEPS), and were further supplemented by targeted sampling of sites in the immediate vicinity of freshwater salmon smolt rearing sites. Taken together these data represent the first national scale examination of the genetic integrity of wild juvenile Atlantic salmon in Scotland in relation to interbreeding with Norwegian farm origin salmon strains.