I always have a can of tuna in the pantry (usually this Hong Kong brand). Always in oil - here soya oil. There is sometimes another brand which is in olive oil. I'll buy that for preference, but haven't seen it for a while.
But I only eat it in the direst emergencies. Like when I've run out of shoes to stew.
Fresh tuna on the other hand, I love. Especially as sashimi.
I've never seen canned salmon here. Not that I'm crying myself to sleep every night craving it.
Edited to add: I've just checked on Taobao, China's main online shopping platform and they have Princes Canned Salmon from England. A 160g can costs ¥64.80 + ¥20 delivery. That's a total of approximately $12.50 USD. I can get another tasty pair of shoes for less!