In large boiler pot over medium heat, melt margarine. To prepare roux, slowly blend in flouer and stir constantly until mixture is light brown. Add onions, celery, garlic and parsley and continue stirring until vegetables are tender. Gradually stir in chicken broth. Add remaining ingredients except seafood. Bring to a boil, then simmer for 10 minutes. Add fish and oysters and simmer for 5 minutes. Add shrimp and cook for 5 minutes more or until all seafood is done.