Mix 2 cups balsamic vinegar, half a cup olive oil, a teaspoon of minced garlic, a teaspoon of thyme, and a half teaspoon of oregano in a large bowl. Add Spanish mackeral fillets, with thier skin still on. Cover, then refrigerate for an hour. Remove the fillets from the bowl, place them on a baking pan, and sprinkle them with capers. Bake for 15 minutes.