Pan-seared striped sea bass is flavored with a blood-orange juice reduction and topped with segments of the fruit and olives. Navel oranges can be substituted for the blood oranges.
Squeeze 3 to 4 oranges to make 1 cup juice; set aside. Remove and discard the peel and pith of the remaining oranges. Using a sharp knife, remove the segments, and set aside in a small bowl.
Sprinkle fish with salt and pepper. Heat oil in a medium skillet over medium-high heat. Add fish, skin side up; cook until golden brown, about 3 minutes. Turn fish over, reduce heat to medium, and continue to cook until fish is opaque and completely cooked through, about 3 minutes. Transfer fish to a serving dish; keep warm.
While fish is cooking, melt 1 tablespoon butter in a small saucepan over medium heat. Add shallots, and cook, stirring, until light golden brown, about 5 minutes. Add orange juice, and bring to a simmer. Cook until juice has reduced by half, about 5 minutes. Remove from heat, and whisk in the remaining 5 tablespoons cold butter, 1 tablespoon at a time. Stir in orange segments and olives. Pour sauce over the fish, and serve immediately.