The Fish Counter

The Freshwater Biological Association own a fish counter on the River Frome in Dorset. Located close to the River Laboratory at East Stoke Fen (NGR SY 867868), the fish counter is built on an Environment Agency venturi gauging weir. The Fish Counter is heavily used by the Game and Wildlife Conservation Trust (who own and maintain the electronics of the counter) in their long-term Salmon monitoring work on the River Frome.

Data on adult Salmon migration through the River Frome are collected by a Scottish Hydro-Electric Mk Xb resistivity counter. The counter is connected to three stainless steel electrodes mounted 450mm apart on the Environment Agency weir. The electrodes monitor the electrical resistance of the water and when a (less resistive) fish or object large enough to bridge the electrodes passes over them the system records a count. The identity of the counts is ascertained by a combination of the pattern of the resistance change (recorded by a purpose designed computerised waveform recording and verification system), video frame-grab and videotape analysis.

The fish counter was first installed in 1973 and forms part of a wider network of fish monitoring sensors deployed across the River Frome system by the Game and Wildlife Conservation Trust. These devices combine to give exceptional data of fish migration through the River Frome system and make the River Frome long term Salmon dataset one of the most comprehensive records of salmon migration in England and Wales.

For further information on Adult Salmon counting on the River Frome please visit the following Game and Wildlife Conservation Trust page: Adult salmon counting on the River Frome