Salmon gets pretty good sized (12-15 lbs. in WalMart). I think it depends on how close to a coast you live. The closer the better chance of finding a whole fish. The further away, you'll only get the small critters (tilapia, catfish, trout, small snapper, etc.) and then just fillets. But whole large salmon is pretty seasonal, and I don't keep track of when it will be available next. You might talk to your local grocer/butcher and see if he can give you some sort of deal in advance of Christmas.