Start by cutting the sea bass filet in thin slices. Put them on a deep plate in which they can be covered in liquid without overlapping.
Mix the juice of half a lemon, half a lime and half an orange and add it to the fish. Put the plate in the fridge for about 15 minutes.
Fennel
Cut the stems off the fennel and cut the fennel in half. Remove the hard core.
Use a mandoline to to cut the fennel in very thin slices.
Grapes
Put the cast iron grill pan on high heat to let it warm up.
Meanwhile, put the grapes in a bowl and add some olive oil and salt to it. Make sure all the grapes are covered well.
Add the grapes to the pan to grill them, while regularly moving the pan back and forth to make the grapes roll. Take them out when the first skins start to burst.
Plating
Put some fennel on each plate first. Then add the fish. Season with salt and pepper to your liking.
Drizzle some olive oil on it, and divide the citrus juice over the four plates.
Carefully divide some wild fennel seeds and some tarragon (fresh if you're able to get your hands on it, but dried works as well) over the plates.
Divide the grapes as well as the small young mint leaves over the plates.