I recently came across a cookbook from the 1850. That cookbook is very interesting covering all types of pioneer cooking. One of the articles covers the preserving of shad, a type of fresh water fish. The recipe used for shad can be used for any fish.
The following recipe is taken directly from the cookbook.
“Clean the shad nicely, place them in layers with back down, and laid open so as the inside of the fish may be up. Sprinkle each fish plentifully with ground salt, and let them stand twenty four hours. This draws out all the blood. Wipe them all dry with clean napkins.
Place them in layers in a clean tub, with the backs down as before. For one hundred shad take ½ lb. saltpetre, and 2 pounds of brown sugar. Strew plenty of rock salt over them with the saltpetre and sugar, there is no danger of putting on too much salt as they will only absorb a certain quantity.”
As you can see, this is a very simple recipe. You will notice this recipe uses quite a bit of salt, I strongly recommend that everybody store at least 100 pounds of salt, if you intend to do any food preserving. Saltpeter or saltpetre is commonly known as potassium nitrate.