Step 1

In a 5-quart saucepan or Dutch oven, heat the oil over medium-high heat. Add the fennel, bell pepper, onion, and garlic to the pan. Season with 1/4 teaspoon each of salt and pepper. Cook until the vegetables are just tender, about 5 minutes.

Step 2

Add the clam juice, the tomatoes with juices, bay leaves, paprika, saffron, and chili flakes. Bring the mixture to a simmer.

Step 3

Add the spaghetti and cook, uncovered and stirring occasionally, until almost tender, about 9 minutes.

Step 4

Add another 1/4 teaspoon each of salt and pepper. Add the clams, mussels, shrimp, and halibut. Cover and cook until the clams and mussels open and the shrimp are pink and cooked through; 5 to 6 minutes. Discard the bay leaves any unopened clams or mussels. Season with salt and pepper to taste. Mix in the parsley and serve.