- In a large pot over medium heat, heat oil. Add onion, celery, salt, pepper and cook, stirring occasionally, until softened, about 5-7 minutes. Add the minced garlic and red pepper flakes. Continue to cook, stirring constantly, until garlic is fragrant, 1 to 2 minutes. 
- Add tomato paste and oregano and cook, stirring, 1 minute. Now add wine, raise heat to medium-high, and cook until cooking liquid is reduced by half, 5 to 7 minutes. 
- Add tomatoes with their juice, bay leaves, clam juice, and stock. Bring to a boil, reduce to a simmer and cook, covered, for 25-30 minutes. Taste and adjust seasoning. 
- Add clams, shrimp, calamari and scallops. 
- Arrange the fish on top of the stew, cover, and simmer until the fish and shrimp are firm and opaque, about 5 minutes more. Discard bay leaves and stir in parsley.