Last week the trust hosted the Institute of Fisheries Management (IFM), for a two-day Electric fishing course. South East Wales Rivers Trust, The West Wales Rivers Trust, The Welsh Dee Trust, The Wye & Usk Foundation, Merthyr Tydfil Angling Alliance attended Pontsticill Village Hall for the classroom-based elements. The practical elements of the course took place on the upper reaches of the Taf Fechan river, where good numbers of Brown Trout and Bullheads were recorded. All attendees were shown the correct practice to Electric fish safely and correctly, using both backpack and control box methods; all attendees passed the exam and achieved certification. The Trust looks forward to putting into practice the knowledge gained on our current project rivers on the Cynon, in the Vale and on the Taff catchment. We would like to thank the IFM, Paul Coulson and Mike Lee for delivering the training, all attendees. Our thanks to Pontsticill village hall for hosting and the Red Cow for providing lunches. (Photos by Harriet Alvis, West Wales River Trust)
Electro-fishing involves creating an electric field in the water that temporarily immobilises the fish or influences the direction in which they swim, making them relatively easy to capture with a net. Electro-fishing surveys can either be qualitative or quantitative. Qualitative electro-fishing is used to capture a snapshot of the fish population, giving an indication of the species present (or any notable absences) and their age classes.
Quantitative sampling requires a more structured approach, with a defined area, typically 100m2, fished repeatedly having been isolated using stop nets at the top and bottom of the river section. This method allows an accurate count of the number of fish and, by recording the species, age and size of the fish caught, the results are entirely comparative between different sites and over time.
Semi‐quantitative electro-fishing is a method that concentrates on recording the presence or absence of different species, the sizes of the fish caught and the abundance of juvenile fish. Unlike quantitative electro-fishing surveys, semi‐quantitative surveys are comparable because they are always undertaken for a fixed time period of five minutes and each site is surveyed with the same level of effort. The advantage of this approach is that it is quick to undertake a survey and so multiple sites across a catchment to be surveyed each year without prohibitive cost implications.
Results recorded from electro-fishing sites across a catchment can be used to assess the distribution and density of juvenile fish, which in turn enables us to estimate the number of adults that were present the previous year and the health of the fish population. The results can also be used to compare tributaries in the same catchment or sections within the same river, which is particularly important in identifying where density is below desired levels and ensures that river improvement works are targeted into the right locations and that any improvements are accurately recorded.