Heat 2 tablespoons of the oil in a large saucepan. Add the celery and onion. Fry over a medium heat until the onion has softened and become translucent. Add the garlic and fry for a further minute. Add the rice and fry for 2 minutes, stirring to coat all the grains in the oil.
Pour the wine into the pan and leave to bubble until all the liquid has evaporated.
Add the stock over a medium heat, a ladleful at a time, stirring continuously. Allow each ladleful of stock to be absorbed before adding the next. Keep adding stock until the rice is cooked but still has a bite to it. This should take about 15–20 minutes. Add the lemon rind and stir in the butter. Finally, add the parsley and season with salt and pepper.
Meanwhile, heat a frying pan over a high heat and add the remaining oil. Season the fish on both sides and place it in the pan, skin-side down. Fry the fish on this side for 3 minutes or until the skin is crispy. Turn the fish over and cook for a further minute. Squeeze a little lemon juice over the fish and serve on top of the risotto.