Sampling of individual adult salmon is used to collect information on the size, sex and age of the fish. This information feeds directly into the stock assessments used for national and international management of Scottish salmon. Sampling of individuals can also provide information on their condition, while examination of scale samples allows their growth history to be investigated.
In Scotland, and other countries, scale samples were historically collected from commercial netting but most of these fisheries have closed in recent years. Due to a lack of sampling information, it has been assumed that there have been no changes in age or size of salmon returning to Scotland since 2018. This is clearly unrealistic given previously documented long-term shifts in the size and demography of salmon in Scotland. To fill this data gap the options for using existing rod fisheries and targeted scientific sampling as a source of biological information on returning adult salmon were investigated.