Abstract: When a signal from a calling device is received by a remote-located fishfinder, the fishfinder emits supersonic waves to a body of water below it and receives reflected waves from a fish shoal as an analog signal. Fish shoal information is expressed by the varying amplitude of the voltage of the signal. The analog signal is converted to Morse code form and sent to the calling device. The Morse signal received by the calling device is converted to the fishfinding information to be displayed. In the transmission procedure in the system of the present invention, analog signals of fish-shoal information are successively converted from analog to digital form. The signals are also converted to respective fish-shoal pulse signals divided on the basis of a given periodical synchronizing pulse and added. The fish-shoal information data are then sampled at predetermined intervals for a plurality of unit signal amplitudes determined along the time base. The data are ordered with bit units and stored in the memory.