Step 1In a large, heavy-bottomed pot, place the fish, water, salt, onion, lemon and orange peels, celery, carrot, parsley and thyme. Bring to a boil over high heat, then reduce the heat to a gentle simmer. Skim any of the scum floating at the top of the stock. Partially cover and simmer for 45 minutes to flavor the stock. Remove from heat, strain the stock and discard the solids. This makes a generous 2 quarts stock.