1) In 6-quart kettle, mix together onion, garlic, parsley, tomatoes, tomato paste, rosemary, and seasonings.
2) Cook on low heat for 2 to 3 hours or until of sauce consistency.
3) Place the crabs, clams, prawns and fish in sauce, and stir in the sherry.
4) Put the lid and simmer for 20 minutes longer.
5) Serve West Coast Bouillabaisse hot with steamed rice.