Clean the barbels, wash them, dab them dry. Sprinkle with lemon juice, season with salt and pepper and turn lightly in flour. Clean, wash and cut leek into rings. Blanch in boiling salted water for about 4 minutes, drain. Heat 2 tablespoons of oil in a pan. Fry the barbels for about 12 minutes, turning them carefully.
Heat 2 tablespoons of oil in another pan. Fry the leek in it. Season with salt and pepper. Cut olives into slices. Serve leek vegetables and barbels with caper apples and slices of olives