Can we (safely?) use salmon after storing it (in deep freeze?) for two years or more? I'm from Poland (in case there is no such thing in other countries) and a few days ago I bought a quark cheese mixed with salmon and some herbs, produced by some German milk factory for one of local big malls network.

When I looked at factory-printed "best before" information, I was shocked. Though actual "best before" date was fine (still a few days left), there was a clearly printed notice that fishing period for salmon fish used for preparation of this quark was in... June-August, 2012.

If this isn't a printer mistake (and there should be a June-August 2014), then what? Can we really safely store (deep freeze?) fish for two or more years? Is it still usable for food preparation processes? And -- finally -- what is the reason for doing so? Wouldn't it be easier and better just to use... a fresh fish?
Yes, if it was still OK when it went into the freezer, and has been frozen the whole time, it is still safe. That's true of all foods - if kept frozen, food will remain safe indefinitely. Quality of taste, appearance and texture are likely to have taken hits in that period of time, however.