From landscapes to freshwater invertebrates: understanding the effects of peatland restoration on Atlantic Salmon (Salmo salar) habitat in the Flow Co

The project will investigate the effects of land-use change on salmon habitat quality via abiotic factors such as physical structure, flow regime and water chemistry (DOC, nutrients and metals), and biotic factors, such as the abundance and diversity of the invertebrate prey base. The hydrochemistry of rivers is affected by many factors, notably water storage and flow pathways, where both water quantity and quality are a function of the interplay between climate, geology, soil types and land use in the catchment (Likens, 2013). The hydrochemistry of rivers also has important relations with the wider landscape and in-stream ecology, including direct impacts on invertebrate communities, and the fish and birds that feed on them (Harrison et al., 2014). In peatland catchments, river water chemistry is typically high in dissolved organic carbon (DOC) but low in nutrients, creating the environment for a distinctive riverine ecosystem, symbolised by the iconic top predator, Atlantic salmon, a species of high conservation and economic importance. Large-scale changes in these catchment, such as peatland restoration, could alter the hydrochemistry of streams that salmon depend on and thus have effects beyond the peatlands themselves (O'Driscoll et al., 2013). The economic value of recreational fishing of Atlantic salmon in Scotland is between £50-100 million (McLay and Gordon-Rodgers, 1997). Some of the most important salmon rivers are in the Flow Country of northern Scotland a rural area, where salmon fishing is a vital element of the local economy (Mainstone et al., 2012). The Flow Country is the largest area of blanket bog in Europe, and of exceptional nature conservation importance (Lindsay et al., 1988). Five of the area's rivers are designated as SACs wholly or partly in recognition of the importance of their salmon populations. In the 1980s, there was extensive afforestation (via drainage and the establishment of non-native conifers) of Flow Country blanket bogs (Stroud et al., 1987). In the last 20 years, with better recognition of the nature conservation and wider values of the area (Hancock et al., 2009; Bain et al., 2011; Wilson et al., 2014), many of these plantations were felled for restoration back to blanket bog. Whilst the terrestrial effects of peatland restoration are relatively well documented, much less is known about the effects of peatland restoration on adjacent freshwater biodiversity. The restoration process can alter the hydrology and water quality (Gaffney, 2016; Gaffney et al., 2018). These effects are likely to alter habitat quality for juvenile salmon and need further investigation (Andersen et al., 2018). In particular, the effects on the riverine invertebrate fauna, on which young salmon, and other riverine species feed, are poorly known.