She is credited with having sunk 3,127 gross register tons of shipping on her single war patrol.

Capelin sailed from New London, Connecticut, on 3 September 1943, bound for Brisbane, Australia, and duty with Submarine Force, Southwest Pacific.

Japanese records studied after the war listed an attack by the minelayer Wakataka on a supposed United States submarine on 23 November 1943 off Kaoe Bay, Halmahera, Indonesia, with the Japanese ship noting the attack produced oily black water columns that contained wood and cork splinters and that later a raft was found.

This is the only reported attack in the appropriate area at that time, and it occurred nine days before Bonefish's apparent contact with Capelin.

Also, Japanese minefields are now known to have been placed in various positions along the north coast of Celebes (now known as Sulawesi) in Capelin's patrol area, and she may have been lost to a naval mine.