Make the broth: Heat oil in a large pot over medium heat. Cook onion and garlic until translucent, about 7 minutes. Add water, wine, celery, fennel, reserved black bass head and bones, canned tomatoes, parsley, thyme, bay leaf, peppercorns, and saffron. Bring to a simmer. Cook, covered, for 45 minutes. Strain through a fine sieve into a clean pot; discard solids.
Make the bouillabaisse: Return broth to a simmer, and add potatoes. Cook until tender, about 10 minutes. Add black bass strips and chopped fresh tomato. Simmer until black bass is cooked through, about 2 minutes. Stir in lemon juice.
Meanwhile, bring a large pot of salted water to a boil. Cook trofie until al dente.
Drain pasta; divide among 6 bowls. Spoon bouillabaisse over pasta. Garnish with parsley.