Making my way through my daily reads, I came across this mention of surströmming on Giornale Nuovo:
"Herring fished in the near-fresh waters of the northern Baltic in spring is processed and canned, but with insufficient salt to arrest all biological activity. In the can, a process of fermentation (some might say putrefaction) takes place, which renders the contents foul-smelling but still edibly non-toxic. Apparently, the hungrily ingenious northern Swedes of yore hit upon this process as a means of economising on the use of salt."