Different stocks of salmon within the Dee, Cowie and Carron rivers comprise the basic units for management and conservation. These stocks are thought to be genetically discrete but at present we do not have information on genetic structuring. To address this the Trust has embarked on a genetics programme to gain an understanding of the stock composition between and within the three rivers so that appropriate fisheries management can be targeted to individual stocks.

Between 2008 and 2010 genetic sampling was carried out throughout the catchments in a strategic manner (see map). This sampling involved the collection of tissue samples from 50 juvenile salmon at each of 50 sites throughout the catchments (a fin clip was taken and then the fish was returned to the river). With these tissue samples a DNA profile of the different sites can be determined. The information from these samples will allow us to build a picture of the distinct breeding populations of salmon within the catchment, which are the basic units for fisheries management.

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Analysis and Initial results

Analysis of genetic material is carried out by staff working for the Rivers and Fisheries Trusts of Scotland (RAFTS) with Marine Scotland Science. Initially, 16 genetic markers called microsatellites were extracted from tissue samples and analysed. Whilst these have shown genetic differentiation of salmon in some rivers in West Scotland, they could not detect differences in samples in the Dee.

In 2010 we embarked on a new technique to develop an alternative type of genetic marker to microsatellites. So far, 6,500 new genetic markers, called Single Nucleotide Polymorphisms (SNP), have been screened. These SNP markers have been screened at three sites in the Dee catchment (the tributaries River Dye, River Quoich and Tarland burn). The SNPs have detected strong genetic differences between these three sites, giving us the first evidence that the Dee's salmon population is comprised of several (or many) smaller, sub-populations.

In the first quarter of 2011 another five sites from the Dee catchment are being analysed for SNPs. The aim is to look at all the SNPs found in the 8 Dee sites and build a best 'marker suite' of 100-300 SNPs that can be used in subsequent analyses. This will reduce costs of analysis and make possible the analysis of the remaining sites.

Phase 2. Adult salmon

The second phase of the genetic sampling programme started in 2010, with the sampling of adult salmon from the rod catch by ghillies and angling club representatives. Adult salmon were sampled by taking a fin clip with a single hole puncher, before being released back into the river. By sampling adult fish throughout the season, we can understand the makeup of different runs of fish entering the Dee and supporting the fishery throughout the year.

The genetic samples taken from adult (rod caught) fish will be compared to the map of the discrete breeding populations (based on results from the juvenile sampling) so that the rod-caught fish can be assigned to a breeding population. This will enable us to identify poorly-performaning or declining sub-populations based on rod catch data. For example, poor rod catches in the month of April could be linked to an area of the catchment. We can then look for problems in this area and proactively manage if necessary.

Biologist taking a tissue sample from a radio tagged salmon; ethanol vials for storing fin clips

The wider context

Genetic samples from the Dee are also contributing to the European SALSEA-Merge project, which aims to map migration and distribution of salmon stocks at sea. This will provide evidence of when and where in the oceans Dee stocks are vulnerable to exploitation.

 Financial support

The Trust is a charitable body and relies on donations to carry out its work. This genetics work has also been funded by RAFTS and grants from the Scottish Government.