In a medium bowl, combine the tuna, capers, 3 tablespoons of the oil, the vinegar, and ¼ teaspoon pepper.
In another bowl, combine the fennel, parsley, ¼ teaspoon each salt and pepper, and the remaining oil.
Cut the baguette in half lengthwise, then quarters or sixths crosswise. Divide among plates. Serve the tuna and fennel salads over the bread.