Take the plastic wrap off of the fish, leaving the paper. Put the fish in a large pot of cold water and add the other ingredients. Bring to a boil and continue boiling gently on a medium fire for 1 1/2 hours. Let the fish cool in the water for about 15 minutes. Remove the fish carefully and place in a container along with the carrots. Refrigerate for a few hours. Serve sliced on individual plates garnished with slices of carrots and prepared horseradish.