Bring a medium saucepan of water to a boil. Add the farro, stir and reduce the heat to low; simmer until tender, 20 to 25 minutes. Drain.
Meanwhile, grate the zest of 1/2 blood orange into a medium bowl. Add the shrimp, fennel seeds, a pinch of salt and 1/2 teaspoon pepper. Toss well, then set aside 10 minutes. Cut the peel off both oranges using a paring knife. Working over a large bowl, cut between the membranes to remove the orange segments so they fall into the bowl. Squeeze the remaining membranes to release any juices. Whisk in 2 tablespoons olive oil and the vinegar; set aside.
Halve the fennel bulb lengthwise and thinly slice crosswise, discarding the core. Add to the oranges along with the watercress, parsley and olives; do not toss the salad yet.
Heat the remaining 2 tablespoons olive oil in a large nonstick skillet over medium-high heat. Add the shrimp in a single layer and cook, turning occasionally, until just cooked through, about 3 minutes.
Add the farro to the salad, toss and season with salt and pepper. Divide among plates and top with the shrimp.