A fish counter network for monitoring Scottish salmon stocks

8. Sites potentially suitable for fish counting

A region-by-region assessment of potential sources of fish count data was undertaken in 2021, using the criteria in Appendix B. Table 2 summarises the outcome of this process. Shetland and Orkney do not have catch records suitable for the assessment of salmon stocks and were not included in this process. Rivers/sites were not assessed for their suitability with respect to the use of hydroacoustic cameras as counters.

8.1. East Region

The East region includes two of the most important catchments for salmon: the Tweed and Tay. However, these systems are too large for counting fish near their outflow points. Whilst the Tweed Foundation operate several Vaki counters, these are on tributaries and not suitable for assessing the condition of the whole river stock. SSE count data from Pitlochry dam were used in the development of Conservation Limits, but the dam is far from the mouth of the Tay and hence unsuitable for assessing stocks. The River Almond (Lothian) has a programme of barrier easement underway and a counter on the recently installed fish pass at Fair A Far weir in Cramond. This would inform on how stocks colonise newly available habitat but would not be suitable for use in the national stock assessments, due to the limited reported salmon catch. The River Teith SAC drains into the Forth at Stirling and the Forth District Salmon Fishery Board have undertaken trials to familiarise themselves with hydroacoustic cameras on the lower reaches of this river. However, the river here is too wide, deep and straight to be suitable for counting fish with hydroacoustics.

8.2. North East region

As noted above, the suitability of data from the counter on the River Ugie is being assessed and a MFS grant has been provided to the Esks Rivers and Fisheries Trust for a hydroacoustic camera to replace the former Marine Directorate fish counting site at Logie Mill on the North Esk. A site at Kinnaird Dyke on the South Esk SAC has been identified as potentially suitable for a resistivity or hydroacoustic counter, but there are currently no plans to install a counter here. Whilst the Dee Trust operate several optical fish counters, these are on tributaries and cannot be used to inform whole-river stock assessments. The counter on the Cowie can be by-passed by fish.

8.3. Moray Firth region

In 2022, the Marine Directorate had a hydroacoustic camera installed on the River Deveron as part of a catchment restoration exercise in partnership with the local rivers trust and the Atlantic Salmon Trust (Project Deveron - The Deveron, Bogie and Isla Rivers Charitable Trust). Data from here will be useful in a national context and artificial intelligence approaches to streamline data processing are being developed (through the MFS grant to Fisheries Management Scotland) that aim to reduce the significant manual effort currently required to turn sonar footage into data on the abundance of salmon. Weirs on the rivers Alness and Balnagown were visited but are not suitable locations for new counters. Data from counters on the River Moriston SAC and the River Beauly are being sought from the operator (Scottish and Southern Energy).

8.4. North region

The Marine Directorate and the Helmsdale District Salmon Fishery Board have jointly operated a resistivity fish counter on the River Helmsdale since 2000. This developed a fault in 2019 and, in 2024, the Scottish Government and the Board invested £300,000 to refurbish the site. The data are currently being validated, but data from here was previously used nationally and are expected to be suitable to do so again. Existing weirs sited low on the rivers Hope, Polla and Thurso were not considered suitable for new counters, whilst the operator of one counter in this region was not willing to make their data availble to the Marine Directorate.

8.5. North West region

Along with the West Coast and Outer Hebrides salmon regions, this a key area for salmon aquaculture and therefore for the monitoring of wild/farmed salmonid interactions and of wild stocks. Marine Directorate installed a new hydroacoustic camera on the River Laxford in 2022 as part of a ten-year catchment restoration project being led by the Atlantic Salmon Trust and Reay Forest Estate (Project Laxford - The Atlantic Salmon Trust). Artificial intelligence approaches to streamline data processing are being developed to reduce the significant manual effort currently required to turn sonar footage into length and abundance data. Data from the Laxford counter are expected to be useful in a national context.

Also, in the North-West region, the rivers Kerry and Badachro were suggested by the Wester Ross Fisheries Trust as being potentially suitable sites for counters. The Badachro fish pass is located close to the sea at the outflow from a loch which buffers changes in river flow and the site would suit an optical fish counter (although there are generally <30 salmon reported caught on the Badachro each year). The fish pass on the Kerry is located on a steep gradient where river flows can be violent and entrained debris would present a severe risk to a counter, making the site unsuitable for a counter.

8.6. Outer Hebrides region

Using funds from a MFS grant, the Stornoway Angling Association have installed an optical counter on the River Creed in 2025 and data have recently begun to be collected for evaluation. The River Grimersta (Langavat SAC) appears suited to a resistivity counter and the Forsa River for an optical counter.

8.7. West coast region

SSE counters on the Rivers Awe and Morar are ideally located to monitor fish populations in this part of the “aquaculture” zone and data from these counters were historically made available to the Marine Directorate. There are few other weirs in the region, although an attempt in the early 1990s to install a resistivity counter on a weir on Islay (Sorn and Laggan assessment area) was not successful.

8.8. Clyde coast region

In 2022, the Marine Directorate installed a resistivity fish counter and CCTV system at Nethermills Weirs on the River Ayr, where a new Archimedes screw micro-hydroelectric generation scheme was being installed. Ayrshire Rivers Trust support the operation of the fish counter, which is hosted by Energy Agency Renewables Ltd. Recent counter validation indicates that the counter detects approx. 50% of salmon using the fish pass and further work is required to obtain a reliable count. In 2008, Loch Lomond Fisheries Trust were provided with an optical fish counter for installation on the Endrick Water by Scottish Natural Heritage (now NatureScot), but parts of the counter were stolen before it could be installed. The weir where it was to be installed is now in a very poor state of repair and is not suitable for use by the Marine Directorate.

8.9. Solway region

Galloway Fisheries Trust (GFT) operate an optical fish counter at the Tongland dam hydroelectric power scheme on behalf of Drax Ltd. GFT provide data to the Marine Directorate that informs the stock assessment for this river. However, there are few fish counts and few catches, affecting the suitability of the data for use in statistical modelling. There are weirs close to the mouths of the rivers Bladnoch (an SAC) and Luce, but both are in poor repair and it would be very costly to make either suitable for the installation of a counter. A previous attempt to install a resistivity counter on the Luce, in the early 1990s, was not successful.

8.10. A fish counter network

Taking into account the above region-by-region review, the expanded counter network could include these new and existing counters: North Esk, Ugie, Deveron, Moriston SAC, Beauly, Helmsdale, Laxford, Creed, Morar, Awe, Ayr and Dee (Figure 2). However, there remain uncertainties on the availability and suitability of data from several of these counters and therefore four further sites have been identifed as potentially suitable for the installation of alternative counters (South Esk SAC, Langavat SAC, Forsa and Badachro). Given the recent experience of obtaining counts from hydroacoustic cameras on the Deveron and Laxford, and the anticipated future use of AI to reduce the cost of doing so, there will be unidentified sites which are suitable for counting salmon using this technology and where local fisheries interests may wish to do so.