Fish cage comprising floating collar (1), net cage and sinker tube (2), wherein a number of strengthening elements (4, 5) are connected to the fish cage, and wherein the sinker tube (2) is connected to the strengthening elements. The strengthening elements comprise vertical strengthening elements (4, 4A) running downwards from the floating collar to the sinker tube, and horizontal strengthening elements (5) running along the circumference of the net cage. The strengthening elements (4, 5) are connected to each other in cross points (11), and the sinker tube (2) is connected to the strengthening elements (4, 5) in such a way that the strengthening elements (4, 5) carry the weight of the sinker tube (2). The fish cage comprises further a number of lines (7) distributed along the circumference, as the lines run from the floating collar (1) to the sinker tube (2), without carrying the weight of the sinker tube when the sinker tube is in its lower position. System for lifting sinker tube of such a fish cage, which comprises a number of lines (7) distributed along the circumference of the net cage, as the lines runs from the floating collar (1) to the sinker tube (2), and at the least one device (8) for tightening and pulling the lines, as an upper end of each line is connected to the device (8) and a lower part is connected to the sinker tube (2).
