MONITORING THE RIVER GARRY
Proving the restoration of flow to the River Garry helps salmon.
Since the “restored” flow on the Garry is still not the full natural flow, it needs to be demonstrated that it is sufficient to allow a healthy self-sustaining salmon population to be established. In particular, the Board is keen to establish how well salmon ascend waterfalls on the river under this flow regime.
The main aim of the monitoring work is therefore to establish how quickly natural salmon production recovers. However, as the Board is also stocking the Garry, this complicates the monitoring. Naturally bred fish must be differentiated from naturally bred fish. (The Board is currently stocking the Garry to ensure there is a run of salmon so that the falls can be tested.)
Since autumn 2017, tissue samples have been taken from all adult broodfish used to stock the Garry. DNA is extracted from these tissues by the University of the Highlands and Islands and genotyped, meaning the progeny of these fish can be identified. In the autumns of both 2018 and 2019, tissue samples were taken from ca. 700 juvenile salmon sampled along the length of the Garry and these are also being genotyped. This will allow stocked fish to be differentiated from wild fish. It will also show how many “families” of wild fish have spawned. This work is funded by SSE.
The information gained above, will also inform standard annual quantitative electrofishing which is undertaken at a number of fixed sites. The numbers of emigrating smolts are estimated using a rotary screw trap at Struan.
Therefore, over the next few years a comprehensive picture should be established of how well a Garry salmon population recovers while at the same time continuing to be supported by the hatchery.