Heat oil over medium-high heat in a large Duch oven. Add onions and garlic and saute until soft but not brown, bout 5 minutes. Add tomatoes, including liquid, wine, basil, and pepper and simmer 20-45 minutes. Add crab, fish and clams and simmer 10-15 minutes longer or until fish flakes easily when tested with a fork, crab is heated through and clams are open. Discard any clams that do not open. Be careful not to overcook. Ladle seafood and sauce into bowls.