White Sea Bass with Orange-Fennel Relish

Eco-friendly choice: white sea bass from the United States-not to be confused with Chilean sea bass.
Combine the first 4 ingredients, 1/8 teaspoon salt, and 1/8 teaspoon black pepper in a medium bowl, stirring with a whisk. Remove the leaves from the fennel bulb; chop the leaves to the size of 2 tablespoons. Remove the stalks. Cut a fennel bulb lengthwise in half; remove the core. Cut the fennel bulb into thin slices. Add the chopped fennel, orange slices, onion, and olives to the orange juice mixture; mix gently to coat. Add the fennel leaves.Preheat a large nonstick skillet over medium-high heat. Sprinkle the fish evenly with the remaining 1/4 teaspoon salt and the remaining 1/4 teaspoon pepper. Add the butter to the skillet; beat until the butter melts. Add the fish to the pan; cook for 4 minutes on each side or until desired browning. Serve with the sauce.