The invention relates to a semi-submersible spar-type offshore fish farm (1) for cultivating fish at open sea, comprising an elongated center column (2) having one of a circular and polygonal cross-section. The elongated center column comprising a first end part (3) and a second end part (4), a buoyancy sleeve (5) and a harvesting sleeve (6) that are coaxially arranged around the elongated center column, wherein the buoyancy sleeve is arrangeable at positions along the elongated center column between the first end part and the harvesting sleeve and the harvesting sleeve is arrangeable at positions along the elongated center column between the buoyancy sleeve and the second end part. Said fish farm further comprises a semi-submersible netted rigid cage(7) that is coaxially arranged around the elongated center column and comprises a first frame (8) that is coaxially arranged around the elongated center column, a first set of elongated connecting elements (9), wherein each of which is arranged to interconnect the buoyancy sleeve and the first frame via at least one detachable and pivotable coupling assembly (10), a second frame (11) that is coaxially arranged around the elongated center column and, in use of said fish farm, is arranged below the first frame, a second set of elongated connecting elements (12), wherein each of which is arranged to interconnect the first frame and the second frame,a third frame (13) that is coaxially arranged around the elongated center column between the first frame and the second frame, a third set of elongated connecting elements (14), wherein each of which is arranged to interconnect the harvesting sleeve and the third frame via at least one detachable and pivotable coupling assembly.
