On 8 February, the submarine began her 11th and final war patrol.   TROUT topped off with fuel at Midway and, on the 16th, headed via a great circle route toward the East China Sea.   She was never heard from again.   On February 29, 1944, TROUT was one of several boats sent to intercept a convoy taking troops to reinforce the Japanese Army on Saipan and Guam. These soldiers were from the crack 29th Division then based in Manchuria. They were being transported in four big transports escorted by what has been described as three of Japan's "best" destroyers: KISHINAMI; OKINAMI and ASASHIMO.

TROUT, now commanded by Albert Clark, just returning from a long overhaul, intercepted the convoy. Clark sank one of the big transports - SAKITO MARU - (7,126 tons) and damaged another - AKI MARU - (11,400 tons).  2,300 of the 4,000 troops on the SAKITO MARU were lost with all their equipment. The three skilled destroyers counterattacked. They claimed a kill - probably correctly.

Japanese records examined after the war indicate that one of their convoys was attacked by a submarine on 29 February 1944 in the patrol area assigned to TROUT.   The submarine badly damaged one large passenger-cargo ship and sank the 7,126-ton transport SAKITO MARU.   These records showed that it was the destroyer ASASHIMO, that delivered the fatal blow.  ASASHIMO was tasked with escorting the SAKITO MARU and, when it was sunk, she detected a submarine and attacked - dropping 19 depth charges.  Oil and debris came to the surface and the destroyer dropped a final depth charge on that spot.   USS TROUT (SS-202) went down with all 81 hands.   On 17 April 1944, TROUT was declared "Presumed Lost".   Now, she's on Eternal Patrol!