"Decoy" was transferred to the Royal Canadian Navy on 1 March 1943 during her conversion and was recommissioned on 12 April with the new name of HMCS "Kootenay" (the ship was gifted to the Canadians on 15 June). After working up, she was assigned to Escort Group C5 for convoy escort duties in the North Atlantic. In April, "Duncan" joined Escort Group B-7. While defending Convoy ON-207 on 23 October, "Duncan", together with the destroyer and a Consolidated B-24 Liberator of No. 224 Squadron RAF, sank . Later the same month, on 29 October, "Duncan" shared the sinking of with "Vidette" and the corvette while protecting Convoy ON-208. Both ships remained on escort duty until May 1944 when they were transferred to the UK in preparation for Operation Overlord. "Duncan" was assigned to the Western Approaches Command, conducting anti-submarine operations, for the rest of the war. "Kootenay" was tasked to protect Allied shipping in the English Channel and the Bay of Biscay and, together with other ships, she sank in the English Channel on 7 July 1944, in the Bay of Biscay on 18 August, and, two days later, west of Brest.