Novel’Dancing Rods’ Behavioural Barrier for the Guidance of Juvenile Salmonids

When fish migrate downstream, they follow bulk flow and unless enough flow is redirected towards a bypass, they need guidance to pass the dam. Guidance relying on behavioural responses by fish are generally less effective but less expensive than physical guidance structures, and hence there is an interest in finding more effective behavioural guidance systems. Here we test a newly developed behavioural guidance system referred to as the 'dancing rods' guidance barrier. The system consists of a series of evenly-spaced parallel floating polyethylene rods that are anchored to the river bottom, vacillating with the flow, thereby presenting the fish will a “permeable wall” whose purpose is to lead the fish away from the turbines. A single pilot trial with 106 out-migrating Atlantic salmon smolts carried out in a large experimental flume showed that the barrier was effective in deterring fish from passing through it. Only 5.7% of the fish crossed the rods barrier downstream, while the rest of the fish remained upstream 51.9%, stayed around the start box or followed the barrier downstream until they reached the end of a bypass ramp 39.6%. Further testing is required to establish the potential of the ‘dancing rods’ as a guiding structure.