Session A3 - Neptun: the electronic guidance system that effectively manages fish movement in a down and upstream waterway.

The protection of fish communities at man-made facilities and barriers has a long history of significant expenditure of scientific and monetary resources. Beyond creating fishways, considerable investment is made to protect fish by blocking their access to turbines, water intakes, and directing them to less risky areas. Nevertheless, guiding fish to the fish passages, especially in downstream direction still present a big problem. The anticipated success of electrical fish barriers and guidance structures has been limited due to current design limitations. However, a device with a fundamentally new design feature has been successfully deployed in Poland. The device is called NEPTUN . NEPTUN is an electric-electronic 3-phase barrier, producing a smooth non-uniform pulsed electric field of low voltage. It uses arrays of positive and negative electrodes and gradually increases the intensity of the electric field between the electrodes from positive to negative. Unlike other devices NEPTUN does not stun fish, but affects their neuromuscular system at the informational level, allowing them to escape from the area of the electric field. The basic field installation consists of steel electrodes attached to the river bottom so that they can move from the vertical to an angle of + / - 90 degrees. A buoy attached at the end of the electrode keeps it in an upright position. Groups of electrodes are powered by remotely controlled generators. Specialized software controls the parameters of the electric field, creates statistically-mastered changes, and controls the switching of each group of electrodes. The system supports sensors for monitoring temperature and conductivity of the water which can be used to automatically adjust the properties of the electric field. With an average power input of 0.43 to 0.45 kWh and electricity consumption of 0.0018 kW/m2, NEPTUN has a low operating cost. Additionally, the system maintenance is minimal