Nearly any food can be preserved through canning, including fish. For the best quality canned fish, use fresh or freshly thawed fish that was frozen immediately after it was caught. With its low acidity, fish needs to be canned using a pressure canner, not with the water bath method. A pressure canner reaches a higher temperature, which is necessary to kill bacteria.
Check the fish carefully for signs of spoilage. Use only fresh or freshly thawed fish.
Remove the viscera, head and tail, but keep the bones and skin intact, if desired. Cut the fish into uniform fillets or cubes. Rinse the fish with cold water and refrigerate it until you are ready to fill the jars.
Wash the jars, rings and lids in hot, soapy water. Inspect the jars for cracks or chips and examine the rings for rust or bends. Discard any with damage and always use new lids.
Pack the fish into the quart jars, distributing the pieces evenly throughout the jar. Leave 1 inch of space between the fish and the top of the jar. It is not necessary to add water, but you can add spices or oil, if you wish.
Wipe the rims of the jars with a clean paper towel. Anything between the lid and the jar has the potential to interrupt the seal. This is particularly true with oily foods. Place the lids on the jars and screw the rings on, making sure they are not too tight or too loose. Read the manufacturer’s instructions on this if you're not sure.
Add 3 inches of water to the bottom of the pressure canner. Arrange the jars in the canner according to the manufacturer’s instructions. Close the lid and turn on the heat. If your pressure canner has variable pressure settings, use the 10 pounds per square inch setting. If your pressure canner does not have variable settings but has a jiggler, it is probably set for 10 psi, but consult the manual to make sure. Once the weight or jiggler begins to move and steam comes through, begin timing the processing. If you have a dial gauge, process the fish at 11 psi and begin timing only when the dial shows this pressure.
Process the fish for 160 minutes -- 2 hours and 20 minutes. Remove the pressure canner from the heat. Do not attempt to open the pressure canner until the temperature drops enough on its own to open. Do not immerse the canner in water to get it to cool more quickly.
Lift the jars from the canner with tongs and set them aside. Allow them to cool to room temperature on their own.
Check the seals about 12 hours after processing by pressing on the center of the lid slightly with your finger. It should not depress. If it does, the jar did not seal properly. Put the jar in the refrigerator and eat the fish within three days, re-process within 24 hours or freeze the fish and eat it within three months.