Melt butter with olive oil in a large pot. Saute onion, celery, and garlic until vegetables are tender. Sprinkle with flour. Stir and cook until light brown. Stir fish stock or clam juice with reserved oyster liquid slowly. Add stock, tomatoes, wine, lemon juice, herbs, and seasonings. Simmer on low heat for 1 hour. Add fish and cook for 10 minutes. Add shrimp, oysters, and crab meat; cook 5 more minutes.