1. In a heavy 3-quart pot, make a roux with flour and butter. 

2. Cut off fire and add onion, bell pepper, celery, and garlic; stir mixture until it stops sizzling. 

3. Add tomato paste.  Heat and stir over low heat for a few minutes. 

4. Add water, stir well, and bring to a boil. 

5. Add Worcestershire sauce and lemon.  Lower heat, cover, and let simmer at least 2 hours, stirring occassionally to prevent sticking on bottom.

6. Season fish and add to mixture. 

7. Bring to a boil, lower fire, and simmer for 1 hour. 

8. Add more water if too thick.  Add green onions and parsley and serve over rice in a soup bowl.