Without adding any oil, toast the pine nuts in an uncoated frying pan until golden brown, remove and set aside. Heat the oil in the same pan. Fry the aubergine for approx. 15 mins., stirring occasionally, season with salt. Remove and set aside.
Heat the oil in a wide pan. Sauté the onion, celery and fennel for approx. 10 mins. Add the tomatoes, olives and sultanas and cook for approx. 5 mins., season with salt. Add the balsamic, icing sugar and reserved aubergine, cover and cook for approx. 15 mins. Combine the caper berries with the reserved pine nuts.
Heat the oil in the frying pan. Season the fish with salt, fry for approx. 4 mins. on each side. Scatter over the oregano, serve with the caponata.