Sonar Fish Counter Trial – River Teith

Non-invasive fish counting technology is hard to come by and most current fish counting technology relies on fish being funnelled into a channel or area to be counted. This severely restricts where fish can be counted as it usually relies on there being a fish pass. Back in February 2018, the Trust with support from the Forth District Salmon Fishery Board worked with a company called Tritech to trial some new fish counting technology on the River Teith near Stirling.

Tritech have developed a sonar fish counter which fires a beam of sound through the water recording how long it takes to return to the sonar unit. It is then able to map and display a picture outlining what it is seeing under the water. This technology can be placed in pools or slow-moving sections of river to count anything which swims through the beam. As the unit is constantly recording, it can detect movement of fish and other aquatic wildlife moving in either an upstream or downstream direction.

When the Trust was trialling the technology, 6 fish were recorded swimming upstream over a 2 day period along with an otter. The below video created by Tritech shows some of the footage which was recorded during the trial. The estimated fish length in this footage was about 80cm long with the otter being 1.2m long. This technology is ground breaking as it can be deployed in a wider range of areas than having to rely on an obstruction such as a weir and fish pass.

Thank you to Tritech for allowing us to trial the technology and a thanks go out to Blair Drummond Estate for allowing the trial to take place on their land.

The below video shows some of the results we managed to capture. 


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