CAN ROACH (RUTILUS-RUTILUS (L.)) BE DEFLECTED BY MEANS OF A FLUORESCENT LIGHT

In response to the large number of fish which encroach on power statio ns, or are damaged at water turbines, an urgent need exists for the de velopment of fish deflection methods to minimise the negative effects of cooling water extraction on fish populations. Behavioural barriers are relatively cheap and easy to install. However, the reaction of fis h to such barriers is often species-dependent and they are therefore n ot always applicable or useful. As a method of nocturnal fish deflecti on, artificial light sources above of under water show most promise. R oach (Rutilus rutilus) are common fish in temperate fresh waters and l arge numbers of juveniles encroach upon power stations during spring a nd autumn. To determine how roach react to artificial lights, their re sponse to a fluorescent light was tested under experimental conditions . Initially, the roach did not avoid the area illuminated by the fluor escent light, but within 10 min they showed a strong preference fbr th e darkest areas of the tank. There are indications that the ability of roach to orientate themselves increases when a light source is presen t, making them better capable of swimming against the current. However , because their initial reaction seems not to be influenced by the lig ht source, the application of this type of artificial light for the de flection of roach may be limited. (C) 1998 John Wiley & Sons, Ltd.