Peel the skin from the whitefish and remove the head and tail. Using a fork, pull the meat from the bones--one side at a time and going from the center of the fish outwards.
Put the meat in a bowl, checking for any bones along the way.
Mix the mayonnaise, lemon juice, horseradish and chopped herbs in a separate bowl. Taste the mixture to make sure it's tangy and herb-y enough.
Mix only enough of the mayo mixture to hold everything together. You may need more of the mayo mixture if the fish is on the drier side.
