Cut the fish into 2 inch lengths and put these in a saucepan with enough vinegar to cover. Bring to the boil, and remove the fish from the vinegar. Have ready a saucepan with a little hot, salted water, to which the sliced vegetables have been added, and poach the pieces of bream in this till tender. Drain, put the fish on a hot dish, sprinkle with the grated horse-radish, well mixed with grated or finely chopped apples, moistened with a little vinegar and mixed with a little sugar. Garnish with slices of lemon.