USS POMPANO was sunk (between 17 SEP 1943 and 05 OCT 1943) with the loss of 77 officers and men while on her seventh war patrol.
Japanese records show that a submarine was sunk in her patrol area on 17 SEP 1943 by air & depth charge attack off the Aomori Prefecture near Shiriya Zaki.
Before being lost, USS POMPANO sank two enemy cargo ships.
The exact cause of her loss remains unknown, but she probably was sunk by the air/sea attack above or fell victim to a mine on or after 25 SEP 1943.
The last ship reported sunk, the Taiko Maru, occurred on 25 SEP 1943, so she probably hit a mine on or after that date but before 05 OCT 1943, when she was scheduled back at Midway.