Cut chiles in half; discard seeds and membranes. Place halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 5 minutes or until blackened. Place in a heavy-duty zip-top plastic bag, and seal. Let stand 15 minutes. Peel chiles; discard skins. Finely chop chiles.
Cook aniseed and cumin seeds in a saucepan over medium heat 1 minute or until toasted and fragrant. Place in a spice or coffee grinder, and process until finely ground.
Heat vegetable oil in a large Dutch oven over medium heat. Add chopped onion and minced garlic; cook 15 minutes or until onion is browned, stirring occasionally. Add the toasted ground spices; cook 1 minute. Add sugar, salt, clam juice, chopped jalapeño peppers, and fire-roasted crushed tomatoes; bring to a simmer. Cook 10 minutes, stirring occasionally. Add chopped poblano chiles, lime juice, tilapia, shrimp, and mussels; bring to a simmer. Cook 5 minutes or until shrimp are done and mussels open; discard any unopened shells. Stir in minced fresh cilantro, and serve with lime slices.