I had the good fortune today to make it as far upstream as Loch Spey, the source of the Spey. Once again the upper Spey missed the recent rain and river levels were low and the moor dry. It is 20km from Spey Dam to Loch Spey and over that distance the character of the river changes frequently. In the stretch immediately below Loch Spey the infant River Spey is a sluggish weedy channel with a sandy/peaty bottom.
Loch Spey is quite small, about 300m long and shallow with weed beds. Plenty small trout could be seen rising in the flat calm conditions. The River Spey begins at the outlet of Loch Spey. This is where the mighty Spey starts, as a 4m wide slow flowing channel with a sandy bottom. The altitude of Loch Spey is 350m, or 1148′, relatively low compared to the source of several of the major tributaries.
One of the main reasons for the visit to the very upper reaches of the river was to investigate habitat suitability. Did salmon ever utilise Loch Spey itself? The sluggish weedy stretch below the loch is only 1.1km long and although that stretch provides no spawning habitat the loch above would have provided a safe refuge for fish waiting to spawn later in the year. It seems likely that in the pre Spey Dam era, when salmon were present in the upper Spey in large numbers, that some of them would have ran as far as the loch to mature before dropping back down to spawn.
Below the confluence with the Allt Coire Bhanain, a tributary with a much larger flow that the Spey itself, the gradient increases and the substrate changes to gravel, pebble and cobble, providing excellent spawning habitat.
From that point downstream there nearly 9km of excellent spawning habitiat, with a succession of riffles, runs and shallow glide. Several tributaries join and the channel width increases to over 25m in places.
In a few areas there was extensive growth of instream weeds, mainly millfoil. In running water this type of habitat can support high fish densities. Plenty fish were observed in the pools, mainly trout and minnows, although no doubt some of the parr were salmon.
Further downstream the character of the upper Spey changed completely. The gradient increased again and the substrate became dominated by boulder and bedrock. For the next 2km there was little spawning gravel although there was an abundance of bouldery parr habitat.
Garva Bridge was as far as I walked today. The section between Garva Bridge and Spey Dam remains to be done but it looks from the road as if spawning habitat dominates again.
It is clear that the upper Spey provides an abundance of first class spawning and nursery habitat. The changes from the slow flowing weedy upper channel into the gravelly spawning habitat, then the steep bouldery stretch highlight the importance of gradient and substrate supply for river channel morphology. The presence of extensive areas of spawning gravels, such as found in the upper Spey, can only exist where the gradient is right, assuming there is an adequate supply of gravels. In this case the gradient of the river in the spawning area is 0.36% over a distance of almost 9km, whereas in the bouldery area downstream it is 1.2%. There is no shortage of gravel input from the many eroding banks in the tributaries and the main stem.
If the habitat is so good why then do our electrofishing results from this part of the catchment show that juvenile salmon are present in very low densities, if they are present at all? Well you don’t need to be Inspector Clouseau to identify one possible reason. Free passage for migratory fish, in an upstream and downstream direction is essential and the problems associated with Spey Dam have been acknowledged by some for a long time. Others remain to be convinced but we hope the that survey work planned for this summer combined with historical data, the Water Framework Directive, and discussions with the dam operator and SEPA will ultimately result in improvements to this vital part of the River Spey