A fish stunning apparatus comprises a fish feed-in device, a fish receiving space, which is loadable with fish in the head first position, a fish positioning means, which engages on the fish head and, for the purpose of stunning the fish, defines a releasable temporary stop position of the fish, said apparatus also comprises a stunning means for acting on the fish head, a trigger device for determining the stop position and for activating the stunning means, and further comprises a control device for controlling operation.;Locations on the fish head which come to rest in the fish receiving space, depending on the size of the head and/or body of the fish, should be positioned optimally for the purpose of stunning. A fish position actuating element can be controlled by means of a fish-size determining device and is connected to a positioning element of the fish positioning means for local adjustment, as a result of which any fish head can be moved automatically, according to the size of the fish, into a consist
