Prepare the seafood. Remove the back shell from the crabs, clean out the gills and guts and cut crabs into quarters. Peel the tail shells from the shrimp, leaving heads on. Wash the clams and mussels well. Cut the striped bass, halibut and lingcod into 1-inch by 1-inch squares. Place fish in a large dish, keeping squid and eel separate. Drizzle fish and squid with 3 tablespoons olive oil and marinate with basil leaves and red pepper flakes.
In a large pot heat oil. Add onion, peppers, garlic, tomatoes, wine, shellfish broth, sherry, herb sachet and mushrooms. Season with salt and pepper. Bring to a boil, reduce heat, and simmer for 1 hour.
Place crab quarters, shrimp, clams and mussels in a layer on the bottom of a large pot. Top with fish, in layers. Add hot broth and taste for seasoning. Add more salt and pepper if necessary. Bring slowly to a simmer and allow fish and shellfish to cook slowly. Remove cooked fish to a platter. Continue cooking shellfish and remove as shells open. Serve in bowls with broth and sourdough bread.
Shellfish Broth: Combine crab and shrimp shells, 1 cup white wine, 2 quarts water and 1 cup of vegetable mirepoix (diced carrots, diced onions and diced celery).