Heat oil in Dutch oven or large saucepan over medium heat. Cook and stir leek, bell pepper, celery, carrot and garlic 8 minutes or until vegetables are crisp-tender.

Add Fish Stock, tomatoes with juice, Worcestershire, thyme, marjoram, bay leaf, salt, if desired, and black pepper. Bring to a boil over high heat. Reduce heat to medium-low; simmer, uncovered, 15 minutes.

Add clams, fish, shrimp and crabmeat to vegetable mixture. Bring to a boil over high heat. Reduce heat to medium-low; cook about 8 minutes or until clams open and fish and shrimp are opaque. Discard bay leaf.

Serve stew in bowls (1 clam per serving) with toasted French bread slices, if desired.

Rinse fish; cut out gills and discard.

Trim tops and roots from onions, leaving most of the dried outer skin intact; cut into wedges.

In stockpot or Dutch oven combine fish skeletons and heads, onions and celery. Add water, lemon, thyme, peppercorns and Herb Bouquet. Bring to a boil over high heat. Reduce heat to medium-low; simmer, uncovered, 30 minutes, skimming foam that rises to the surface.

Remove stock from heat and cool slightly. Strain stock through large sieve or colander lined with several layers of damp cheesecloth, removing all bones, vegetables and seasonings; discard.

Use immediately or refrigerate stock in tightly covered container up to 2 days or freeze stock in freezer containers for several months.