Abstract: Echo ranging apparatus to locate fish, vegetation and structure in the sea modifies signals presented to a recorder in the apparatus so as to enhance the capability of the user to distinguish fish in the vicinity of vegetation and structure, including the sea bed. A transducer receives the reflected echo signals. A receiver stage and amplifier stage present signals which, apart from the modification, would be conventionally useful in aiding the user to locate fish. However, a signal modifier connected at the output of the amplifier stage, between the amplifier stage and the input to the recorder, substantially enhances the capability of the apparatus. It does so by shunting signal reducer circuitry in parallel at the output of the amplifier when the level at the output surpasses a predetermined level, to reduce the signal levels at such output while retaining variations in such signal levels. Such retention, as opposed to, e.g.