A cast iron skillet presents several options for cooking fish. However, fish oil can seep into the iron, leaving your skillet with an unpleasant fishy odor that can permeate other food cooked in the skillet. You can eliminate fish odor from your cast iron skillet in a number of ways.
Charring and Treating
Sauté several onions and garlic cloves in the skillet and char them until black.
Bits of the charred onions and garlic will form a layer on the surface of the skillet; let the skillet cool and scrape this debris from the surface.
Treat the inside of the skillet by applying several layers of a mixture of salt and vegetable oil, let it stand for several minutes, and clean the skillet.
Scrubbing and Re-seasoning
Wash the pan with strong soap and hot water.
Scrub the inside of the skillet with a light abrasive, being careful not to scratch it. Dry with paper towels.
Re-season the skillet by rubbing a thick layer of vegetable shortening on the inside and baking the skillet in an oven at 250 degrees for two hours.
Boiling Liquid
Empty a can of tomato juice or tomato sauce, or a mixture of one cup of vinegar and four cups of water, into the skillet.
Bring the liquid to a rolling boil, reduce heat and maintain a low boil for 20 to 30 minutes.
Remove the skillet from heat and discard the contents. Clean the skillet and re-season it, if necessary.