Combine first 4 ingredients in a medium saucepan over medium-high heat. Bring to a boil; stir in couscous. Remove from heat; cover and let stand 5 minutes. Stir in tomato, 2 tablespoons oil, grated lemon rind, chopped tarragon, and sea salt; cool to room temperature.
Brush 1/2 tablespoon oil onto bottom of large roasting pan. Open trout; stuff each evenly with couscous mixture. Close fish to enclose the stuffing; tie fish securely in 2 places with heavy string. Tuck a sprig of tarragon under string of each trout. Carefully place trout in pan. Brush with remaining 1/2 tablespoon oil; sprinkle evenly with pepper.
Bake at 425° for 12 minutes or until cooked through at thickest part.
Remove trout to a serving platter, and cover with aluminum foil. Place roasting pan across 2 burners over medium heat. Add wine, stirring to loosen particles from bottom of pan. Bring to a boil, and reduce to 1/4 cup. Remove from heat; add butter, parsley, and capers, stirring just until melted. Stir in lemon sections. Spoon over trout.