Here's a gumbo recipe for shrimp and okra (yuk). I'm leaving the okra part out, and you can certainly add your tuna and the chicken to this.
Make a roux (equal parts flour and fat--keep stirring until smooth and golden--stir longer if you want a darker roux).
Add onion, celery and pepper to roux and cook until limp.
Add diced tomatoes and cook for 10 minutes.
Add 2 quarts chicken stock, 2 bay leaves, 1/2 t thyme, Tabasco, 1 T Worcestershire sauce.
Cook for 30 minutes
Add shrimp and chicken and boil for 5 minutes.
Stir in 1/2 cup parsley and green onions.
Serve over hot boiled rice.