Your question: Canned sardines taste good to me but they have a rotten smell once you open the can and leave it around for a while. Can rotten smell be any good? What happens to the sardines after you eat them? Do they rot?
Answer: In Nature everything must be able to Decay into Organic matter for the cycle of Life to go on !
Is it so odd that sardines would be able to do the same thing ?
The rotten smell that you are smelling after the can has been sitting around for awhile is just the Natural process of the cycle of Life taking place !
If they did not Rot and Decay, then the body may not Digest them properly ?
When folks talk about eating a Tender steak, what do you think has happened to this steak to Tenderize it ?
The Bacteria have begin to Decay the Meat and make it Tender, is all that may be taking place, and you just eat it before it is all processed by the Bacteria into Decayed matter !
How about that for food for thought ?
Smile Tis your choice.