The Dollar Burn, a tributary of the River Devon, looks at first glance like an excellent spawning and nursery burn for salmon and sea trout. With crystal clear water straight off the Ochill Hills and pristinely clean gravel substrate, it might be expected to support the same favourable levels of production as its near neighbours, the Menstrie and Alva Burns. However, since monitoring by the Trust commenced in 2011, the Dollar Burn has returned disappointing densities of juvenile salmon, and no salmon at all were caught there in 2014, 2015 and 2016. This compares poorly with the Menstrie Burn, where we have recorded densities of 90 salmon per 100m2 and 38 per 100m2 in the Alva Burn. Fluctuations in production between years is expected, but to find three years in a row where zero juvenile salmon were found suggests that something is going on!
It is likely that salmon production in the Dollar Burn was being hindered by two old weirs downstream (see photos), one near the mouth of the tributary (Dollar Burn Water Race), and one further downstream on the main stem of the river (Dollar Weir). It would seem that while some salmon were found upstream of these barriers, so few adults would get through that the available habitat was not at all well utilised for producing the next generation. To test if salmon were reaching as far up as the Water Race, we electrofished immediately downstream of it. The picture was better than it was up in the village, but densities were still very disappointing at less than 10 per 100m2.
In the Autumn of 2015, two projects to renovate and improve fish passage on these structures were completed. The Dollar Burn Water Race was refurbished by the Ochils Landscape Partnership, while Dollar Weir was improved by the Trust using funding gratefully received from Scottish Water, Clackmannanshire and Stirling Environment Trust and the Devon Angling Association. The results of the works certainly looked very smart (see photos), but would they work as we hoped, and improve salmon production in the Burn?
We monitored in summer 2016, one season after the improvement works, expecting to find some young of the year salmon fry in the Burn, but the picture was unfortunately very similar to that before the works. Then, in the winter of 2016 Trust staff and members of the angling club began to report seeing a large number of redds (salmon nests) in the main stem of the River Devon upstream of Dollar Weir. This gave us hope that spawning activity was high, and when we electrofished in summer 2017, we found the highest densities of salmon yet seen in the Dollar Burn. Just below the Water Race, we recorded 64 salmon per 100m2.
Its early days, but we are hoping this is the start of an improving trend in the Dollar Burn rather than a blip. The same improvement is yet to be observed upstream of the Water Race, but we are cautiously optimistic that if more adults are accessing the Dollar Burn, some may start to make it up into the village to spawn there. In the meantime, we will keep monitoring!