Device for holding and positioning equipment at fish cage (1) having mainly circular, horizontal cross-section comprising at least one buoyant ring (7) and a seine (8) attached directly or indirectly to the buoyant ring (7). The device comprises a crossbar (2) arranged diametrically across the fish cage (1), the crossbar comprising at each end a support structure (10 resp. 11) equipped with wheels (26) running on a rail (3) arranged to the buoyant ring (7) of the fish cage (1). The crossbar (2) is arranged to be rotated over the fish cage (1) by simultaneously moving the support structures (10, 11) along the rail (3), the crossbar (2) being provided with an automatically adjustable bearing arm (29) to compensate for deviations from prefect circularly shape of the fish cage (1) when the crossbar (2) is rotated.
