Advancing behavioural guidance systems to help conserve the European eel (Anguilla anguilla)

This study investigated yellow (experiment 1) and silver-phase (experiment 2) European eel (Anguilla anguilla) behavioural response to pulsed direct current electric fields. Eel were offered a choice of two channels through which to pass under either: (1) a treatment condition, in which eel could select either an Electrified Channel (EC) or one in which the electric field was negligible (Non-Electrified Channel - NEC), or (2) a control in which the electric field was absent in both routes. In experiment 1, the influence of the EC field strength and direction of approach (upstream or downstream) on both initial and total channel passage and avoidance (reaction, route change and rejection) was assessed. In experiment 2, the influence of EC field strength and pulse frequency on initial channel passage and avoidance was investigated. The percentage of eel that passed the NEC under the treatment did not differ from the control in either experiment. In experiment 1, yellow-phase eel exhibited greater total avoidance in the EC when travelling upstream; but field strength had no effect. In experiment 2, silver-phase eel exhibited greater initial avoidance in the EC, but neither field strength nor frequency were influential. These findings will help optimise the design of devices that employ electric fields to guide eel.