Heat oil in a Dutch oven over medium heat. Add onion and celery; sauté 10 minutes or until tender. Add potato and next 4 ingredients (potato through broth). Bring to a boil; reduce heat, and simmer 20 minutes or until tender. Place potato mixture in a blender, and process until smooth. Return puréed mixture to pan; stir in wine and milk. Cover and cook over medium-low heat 15 minutes, stirring occasionally. Add lemon juice and fish; cook 10 minutes or until fish flakes easily when tested with a fork, stirring frequently. Sprinkle with parsley.