Police are trying to trace the man following the robbery at Heron Foods in Great Bridge.
Officers say the offender placed tins of fish in a carrier bag and attempted to run from the shop with the cans.
A man who witnessed the theft attempted to stop him.
The member of the public was punched twice in the face after he attempted to grab the bag from the robber, and fell backwards, hitting his back on a metal crate.
The incident happened on Wednesday, February 24, at around 5.40pm.
West Midlands Police is urging anyone who recognises the man in the images to contact officers through Live Chat at west-midlands.police.uk (8am to midnight) or call 101 anytime, on 0800 555 111, and quote crime number 20SW/55774H/21.
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org