Heat the oil in a very large pot over medium heat. Add the fennel, onion, shallots and salt. Sauté about 10 minutes. Add garlic and red pepper flakes. Continue to sauté for a couple of minutes. Add tomato paste, tomatoes with juices, wine, fish stock and bay leaf. Cover and simmer for 30 minutes to allow flavors to blend.
Add clams and mussels to the cooking liquid, cover and cook about 5 minutes. Add shrimp and fish. Simmer until the fish and shrimp are cooked through and the shellfish open. About 5-8 minutes longer. Add more salt or red pepper flakes to your taste. Ladle into large bowls and pour your self a glass of Portalupi Arneis!!