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National Electrofishing Programme for Scotland

The Conservation of Salmon (Scotland) Regulations 2016 were introduced to manage the killing of Atlantic salmon in inland waters based on an annual assessment of the conservation status of stocks. Conservation Status is determined using an adult based assessment method. However, there is increasing interest in developing a new juvenile assessment method to complement the existing approach.

Electrofishing surveys are undertaken by fisheries managers, scientists and regulators to capture and count juvenile fish, primarily in rivers. Where electrofishing is performed according to carefully defined standard operating procedures (SOPs) and combined with appropriate statistical analysis, it is possible to estimate the number of fish in a particular section of a river, or by upscaling, the total production of fish in a river or region.

Electrofishing data are one of the most commonly collected sources of information on the status of freshwater fish populations. However, they are not currently used to assess the status of salmon stocks at a national level because (1) until 2018 there has been no strategic, statistically designed national electrofishing programme, and (2) the analysis and interpretation of electrofishing data is associated with substantial technical challenges.

Marine Scotland has undertaken a programme of research to address these challenges, with the overall aim of developing a juvenile assessment method that can be used to determine the status of salmon populations at a range of spatial scales, from individual electrofishing sites to catchments and regions. The objectives of this research are as follows (see also Figure 1):

  • Collate and quality control historical multi-pass juvenile salmon electrofishing data for Scotland.

  • Develop methods to characterise habitat variability across Scottish rivers using landscape derived proxies that can be determined from spatial (e.g. digital mapping or digital terrain models) or remotely sensed data.

  • Model the spatial and temporal variability of the capture probabilities of salmon fry (<1 year old) and parr (≥1 year old) from multi-pass electrofishing data.

  • Model spatial and temporal variability in the densities of salmon fry and parr and develop a benchmark for healthy salmon populations that can be used for assessment.

  • Produce a strategic national electrofishing strategy (The National Electrofishing Programme for Scotland) to provide a quantitative, unbiased estimate of the number of salmon in Scotland’s rivers.

  • Develop a set of standard operating procedures to ensure consistent minimum data collection and data entry standards.

  • Develop approaches for scaling electrofishing observations to catchment or regional scale estimates of salmon production.

  • Develop an assessment approach that compares observed salmon densities with a benchmark indicative of healthy populations.

The National Electrofishing Programme for Scotland provides the data necessary to assess the status of Scotland’s salmon stocks using electrofishing data.

Electrofishing Scotland Network - aims