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The River Cononish is the headwater of the River Dochart
– the symbolic source of the River Tay and the
area which produces some of the earliest spring salmon
for which the Tay was famous. Surveys in the 1990s and early 2000s indicated
juvenile salmon populations were very poor and local anecdote
suggests brown trout have greatly declined in 30 years.
It was not clear why that should have been so as the general
quality of the habitat is good. Given the importance of this area the Tay Foundation
supported an investigation to establish the cause of
this problem. In the first instance the invertebrate
community was investigated to see whether there
might be some subtle water quality issue.
That survey, conducted in 2006, showed that in summer the abundance of invertebrates in the upper Cononish was low but the species present were representative of what might be expected in that type of environment. Numbers of juvenile salmon were low in the same area, even where artificial stocking had taken place. However, a few km downstream, below the village of Tyndrum, invertebrate abundance was much higher and the species assemblage indicated what might be considered to be some evidence of "enrichment", perhaps as a result of discharge from Tyndrum sewage works. However, at that point the density of naturally spawned juvenile salmon was high and growth rates were surprisingly high for such an environment. The apparent enrichment appeared to be having a significant benefit for the salmon population.
The report of the survey can be obtained by clicking here.
Since 2006 electrofishing surveys have continued to be conducted annually in this area, the results of which are published elsewhere on this website. The Tay District Salmon Fisheries Board has continued to stock parts of the Cononish with eyed salmon ova and fry derived from reconditoned kelts originally caught in the Fillan Water. Since the 2006 survey the density of juvenile salmon has in fact increased in the Cononish but their growth rates have fallen markedly suggesting the stocking experiment has had the effect of saturating the habitat with fish, although densities are still lower than in the Fillan Water where densities and growth rates have remained at the same high level. These results confirm that the upper Cononish is not as productive environment and does not have as high a carrying capacity for salmon as the Fillan, but it is perhaps still not entirely clear why salmon were almost non-existent in the upper Cononish even up to the early part of the stocking experiment.
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The Cononish is the symbolic headwater of the Tay,
whose source rises on Ben Lui seen in the background.
The fish population in this area has declined and investigations
were aimed at finding out why. |
