Thaw fish, if frozen. Rinse fish; pat dry. Cut fish into 4 serving-size pieces, if necessary; set aside. Snap off and discard woody bases from asparagus. Cut asparagus in half; set aside.
In a 10-inch skillet combine 1 cup of the broth, the lemon peel, and black pepper. Bring to boiling; reduce heat. Carefully add fish and asparagus. Cook, covered, over medium-low heat for 4 minutes. Add sweet pepper strips. Cook, covered, 2 minutes more or until fish flakes easily when tested with a fork. Using a slotted spatula, transfer fish and vegetables to a serving platter, reserving liquid in skillet. Keep fish and vegetables warm while preparing sauce.
For sauce, stir together remaining broth and cornstarch. Stir into liquid in skillet. Cook and stir until thickened and bubbly. Cook and stir for 2 minutes more. Stir in chives. Arrange fish and vegetables on couscous; spoon sauce over top. Makes 4 servings.