Grease a non-stick ovenproof dish with a little olive oil and lay the potatoes, carrots and onions in layers. Sprinkle with the finely chopped celery and add salt and pepper. Rinse and dry the slices of fish.
Place the fish on top of the vegetables and add a bit of salt and pepper. Pour the remaining oil and the wine on top and cover with foil. Cook in the oven for 50 minutes. Remove the foil and continue to cook for 10 minutes more.
Squeeze the lemons and pour the juice over the fish, then move the dish around so that the juice goes everywhere. Serve the slices of fish and the vegetables in their sauce.