Place the oil in a pot set over medium heat. Add the onion, strips of fennel and garlic and cook 3 to 4 minutes to soften. Add the tomato paste, diced tomatoes, nectar or stock and wine. Simmer the mixture 5 minutes, or until the fennel is tender. Stir in the seafood, return to a simmer, and simmer 4 minutes more, or until just cooked through. Stir in the pepper, fennel leaves or parsley, and serve.