Preheat oven to 400 degrees F.
To make the croutons lightly brush the baguette slices with olive oil and bake until crisp, about 10 minutes.
To make the fish stock, hack up the crabs with a large sharp knife and put them into a big stockpot. Peel and de-vein the shrimp and put the shells into the pot (reserve the shrimp for later). Add the fish bones on top. Add lemon and lemon juice, bay leaves, fennel, strip of orange zest, parsley, and thyme. Add the tomatoes, squeezing as you add them. Add garlic, leek, onion, water, and wine. Season with sea salt and freshly ground pepper and a pinch of cayenne. Place over a medium heat. Simmer gently for 30 minutes, stirring occasionally, but don't let it boil. Skim and discard the fish foam that rises to the surface. Remove from heat.
Put the lobster claws into a large cast iron serving pot and strain the stock over them.
Turn the temperature up and simmer for 5 minutes. Add a splash of olive oil and a pinch of saffron. Lastly add the reserved shrimp and lobster tails, and cook for 3 minutes. Add large bite sized pieces of sea bass and cook for 3 minutes.
To serve: Place pieces of seafood in a big soup bowl. Put a spoonful of Rouille on Croutons and ladle soup on top.
*Cook's note: You can also use non-oily fish such as Snapper, Halibut, Grouper, or Monkfish
To make the rouille, put the red pepper, garlic, mayonnaise, saffron, cayenne, and lemon juice in a food processor. Pulse the mixture until combined and smooth. Season with sea salt and freshly ground black pepper.