Wash all fish and seafood, except crab and pat dry.
In a heavy-based pot, add olive oil and onion and saute until translucent. Add fennel and cook for 5 minutes, then stir in white wine and garlic and simmer for 10 minutes.
Add orange zest, saffron, tomato juice and stock, and simmer for another 10 minutes.
Nestle fish fillets and seafood into the sauce, covering them with the liquid. Put a lid on the pot, bring back to a simmer over a medium heat and cook until clams and mussels open, about 10 to 12 minutes. Season with salt and pepper and serve garnished with fresh basil.