I have one and have used for all sorts of things homemade salami, ground beef, mozzarella cheese (I buy bulk) etc. last year I tried peppers that are as fresh as the day I put then in.
One thing you have to remember that they use 'special' bags or a roll that you can make custom bags yourself.
Great gadget to have and I'm sure it will work for fish.
Her is a link on how long things last. Hope this helps.
http://www.stilltasty.com/