Earth currents as a cause of fry losses in a trout stock

The grounding of the mains by the energy suppliers causes sporadic alternating earth currents. From water over the housings of areator and its earth-connected guardwire such currents may occur. In a South German trout hatchery these earth currents led to losses of 30% among the influenced fry and to a 25% crippling among the surviving fry. Cause, clinical events and possible preventive measures are discussed.