1. Preheat oven to 400°.
2. Combine potatoes, 1 tablespoon oil, and 3/8 teaspoon salt on a baking sheet coated with cooking spray; toss well to coat. Bake at 400° for 15 minutes. Stir potatoes; bake an additional 10 minutes or until golden brown and tender. Combine 2 tablespoons oil, juice, shallots, paprika, garlic, and 1/4 teaspoon salt in a large bowl, stirring with a whisk. Add hot potatoes to bowl; toss to coat.
3. Heat a large nonstick skillet over medium-high heat. Pat sardines dry with paper towels; sprinkle with remaining 3/8 teaspoon salt. Add remaining 2 tablespoons oil to pan; swirl to coat. Add sardines to pan; cook 3 minutes on each side or until crisp and done.
4. Arrange about 1 1/2 cups arugula on each of 4 plates. Remove potatoes from dressing with a slotted spoon; arrange about 3/4 cup potatoes on each serving. Drizzle remaining dressing over salads; top each with 2 sardines. Serve with lemon wedges; sprinkle with pepper.