In this riff on bouillabaisse, pasta shapes are added to the broth just before the dish is served. Ask your fishmonger to fillet the fish, reserving the head and bones of one for the broth.
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.