National Electrofishing Programme for Scotland

Water quality sampling

Water quality directly and indirectly affects fish survival, performance and productivity (numbers or biomass). To date it has not been possible to incorporate water quality into existing juvenile density models due to a lack of spatially extensive water quality data, particularly in upland and remote areas. The National Electrofishing Programme provides an opportunity to collect water quality samples across Scotland, including remote areas. Although the samples will only provide a “snap shot” in time, it is expected that large-scale patterns of inter-site variability should be clear as most of the electrofishing will be undertaken under comparable summer low flow conditions.

The samples will be analysed in Marine Scotland’s UKAS accredited water quality laboratories at the Freshwater Fisheries Laboratory over the summer months. Data analysis will then be undertaken to determine (1) whether it is possible to produce large scale models for Scotland to predict major spatial differences in water quality (2) whether water quality models can improve predictions of juvenile salmon abundance.

Previous collaborative research between Marine Scotland, the River Dee Trust and University of Aberdeen on the Aberdeenshire River Dee suggest it is possible to produce informative water quality models from spot sample data that could be used in fisheries assessment (Figure 1). The work conducted under The National Electrofishing Programme will further explore these issues at the national scale.

Map showing the modelled variability in nitrate concentrations (µeq l-1) across the Aberdeenshire River Dee. Open squares show water sampling locations, lines show rivers. Colours indicate observed (squares) or predicted (lines) nitrate concentrations. Line widths show river size by Strahler river order (wider lines show higher river orders indicative of larger rivers)