Add onion and celery; saut 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 pured 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.