Step 1In a medium saucepan, heat the olive oil over medium heat. Add the onion and bell pepper and cook until soft, about 5 minutes. Add the crushed red pepper, fennel and one-half of the garlic and cook until fragrant, about 3 minutes. Stir in the tomato paste and cook about 3 minutes. Add the red wine and simmer until it is reduced by a third to a half, about 20 minutes. Add the crushed tomatoes, salt, bay leaf, oregano and pepper and cook at a low simmer until the sauce is a dark brick red, about 45 minutes. You should have a little more than 6 cups. (The recipe can be prepared to this point up to 2 hours in advance or even further if tightly covered and refrigerated.)
Step 2While the sauce is simmering, cut the meaty fish and flaky fish into bite-sized chunks, keeping separate. Season both types of fish and the shrimp with the remaining chopped garlic and a little salt, cover tightly and refrigerate.
Step 3In a separate large saucepan, one that is taller than it is wide, arrange the fish. First, ladle in a thin layer of the sauce. Then arrange the cracked crab in a layer. Begin stacking the fish on top of that in the order of how long they will take to cook: start with the meaty ones, then the flaky, then the shrimp and then the clams and/or mussels.
Step 4Pour the remaining sauce over the fish and give the pan a good shake to distribute the sauce evenly. Cover and place over medium heat. Cook until the clams and mussels are open, about 20 minutes. From time to time, shake the pan vigorously (hold the lid on tight!) rather than stirring, to avoid breaking up the fish.
Step 5When ready to serve, taste and add more salt if necessary, gently stir in the parsley and ladle the stew into warm bowls.