A predator deterrent system 1 for deterring predators of aquatic creatures such as fish 44 in submerged fish farms comprising a control means 132 for controlling delivery of power to the at least one electrified enclosure section 40A-40H. Each enclosure section may be provided with two or more conductors and the control means is configured to supply power to one conductor following removal of power from a preceding conductor. The control means is further configured to supply power to an electrified section following removal of power from a preceding section. Also claimed is a predator deterrent system comprising at least one trigger device 28 configured to detect a predator 46 in the vicinity of a fish enclosure 10 and configured to generate an alarm signal responsive to the detection of the predator and at least one alarm device responsive to the alarm signal generated by the trigger device, the alarm device comprising at least one electrified enclosure section wherein upon receipt of an alarm signal generated by the trigger device at least one electrified enclosure section is powered. Control means may be provided and the trigger devices may be motion detectors or sonar detectors. The enclosure may be an electrified net.
