Cut sea bass into single sized pieces.
Soak mushrooms in cold water.
Heat the olive oil in a saucepan. Sauté the onion, garlic, mushrooms and green pepper. Cook for 3 minutes. Add the tomatoes and let cook for 2 minutes. Add tomato paste, red wine and 5 cups of broth from mussels and clams. Add salt and pepper, cover and simmer for 45 minutes.
Arrange the seafood in a large kettle adding first the fish then the shrimp.
Separately, bring the sauce to a boil. Then pour the sauce into the kettle. Cover and cook on low heat for 10 minutes. Add the mussels and clams. Cover and cook for 5 minutes, until the shellfish open and release their liquor.
Ladle into soup bowls and server immediately.