Passive electrolocation is a process where certain species of fish or aquatic amphibians can detect electric fields using specialized electroreceptors to detect and to locate the source of an external electric field in its environment creating the electric field. These external electric fields can be produced by any bioelectrical process in an organism, especially by actions of the nerves or muscles of fish, or indeed by the specially developed electric organs of fish. Other fields are induced by movement of a conducting organism through the earth's magnetic field, or from atmospheric electricity.