You might want to consider getting yourself one of those vaccuum sealers, you know the ones that suck all the air out of the bag and package the food inside the bag? There's one on the info-mercials called the Foodsaver or something like that, I hear a lot of guys using it for their tuna. So, you can vaccuum seal the fish, or you can also get a canner, or have it canned. Another option is to smoke it. You can get it smoked at a lot of the landings in SD I believe, or you can buy yourself a smoker for pretty cheap.
-Brian