1. Preheat the oven to 350 degrees. Coat a baking sheet with cooking spray. Brush the bread slices with 1 tablespoon of the olive oil and place on baking sheet. Bake 15 minutes, turning once halfway through. Set aside.
2. In a soup pot, heat remaining oil over medium-high heat. Add the fennel, onion, bell pepper, garlic and fennel seeds. Cook, stirring occasionally, 7 to 8 minutes.
3. Add the tomatoes, potatoes, clam juice and water; gently boil 8 minutes or until potatoes are nearly cooked through. Reduce heat to a gentle simmer and add the fish. Cook until fish is no longer translucent, about 3 minutes. Add the shrimp and cook 3 minutes; add the clams and cook 2 minutes more. (If using fresh clams, cook until they open, about 10 minutes.)
4. Place the toasts in the bottoms of four soup bowls; ladle soup over bread. Serve.