Some fish test their environment by generating electric fields outside their bodies. To send and receive electric signals, one's own or those from a neighbour, is the basis of some bony fishes' unusual sensory capacities that enable them to lead a secret, nocturnal life. This volume provides the reader with a detailed account of these fishes' biology and behaviour and their sophisticated sensory capacities. The phylogenetic relationships of the fish taxa involved are discussed as well as the physiology and anatomy of the electrosensory-motor system and its integration to form an efficient intelligence system. The main emphasis is on the descriptive and experimental analysis of electric communication behaviour in a variety of species, including studies of digital signal synthesis. Whenever possible, mechanisms of communication are indicated.