An apparatus for protecting aquatic animals, particularly elver the juvenile form of the eel, from a water pumping device is disclosed. The apparatus includes a screen with a multiplicity of apertures of predetermined size which allow water to pass from an outer side to an inner side before reaching a water pump. There is a first sensor for measuring the water level on either the inner or outer sides of the screen and a second sensor for determining the difference between the water level on the inner and outer sides of said screen. The apparatus further includes a processor for controlling the pumping rate of the pump varying the rate of pumping depending on the water level measured and on the difference between the water levels.
