Independent Ecological Consultancy
Gleann Beag salmon restoration
Client Scottish and Southern Energy
Gleann Beag is in the headwaters of the River Carron in Easter Ross. An intake weir prevents salmon access into some 5km of the upper glen. Waterside Ecology was contracted to assess the potential benefits of re-opening upper Gleann Beag to salmon.
The approach taken was to quantify available habitats upstream from the weir, identifying suitable areas for each age class of salmon from eggs to adults. Mapping the distribution of these habitats allowed us to determine whether, for instance, spawning habitats were distributed in a way that would permit young salmon to migrate into all available juvenile habitats.
Stratified electric fishing in similar habitats downstream from the weir provided indicative densities of parr that might be expected were access made possible. Scale reading showed that parr were slow growing and multiple year classes were present. This pattern is often consistent with early running, multi-sea winter stocks. Combining the field data sets with information from literature reviews on over-winter survival and smolt production allowed the potential increase in smolt output from allowing upstream access to be evaluated.
Ultimately, the potential benefits of increased smolt output will have to be balanced against the cost of modifying the barrier, to determine whether a fish pass should be installed. The project is a classic example of how scientific survey and research can be used to provide the tools for objective decision-making in fisheries and wildlife management.