Place a large pot over medium-high heat. Add the olive oil, diced onion, diced celery, and diced fennel. Cook for 5 minutes over low heat, stirring occasionally. Add the minced garlic, bay leaf, and lemon peel. Continue to cook for 5 minutes over low heat, stirring occasionally.
add the tomato and fish stalk
Roughly chop the tomatoes and add them to a pot along with the tomato sauce and wine. Stir, and cook for 5 minutes at high heat for the alcohol to evaporate. Pour in the fish stalk, add the parsley, season with salt and pepper, and continue to cook for 10 minutes.
cook the potatoes
While the fish stew is cooking, cook the potatoes separately. Peel the potatoes and cut them into larger pieces, approximately 2 cm x 2 cm (1-inch x 1-inch). Add to a pot of salted boiling water. Cook for 12 - 14 minutes or until the potatoes are almost cooked.
add the fish to the stew
Add the mussels, shrimp, and drained potatoes to the pot with the vegetables and liquid. Stir, then place the fish fillets on top. Gently dip the fish into the stew until at least half covered in liquid. Cover with a lid and simmer for 8 - 10 minutes, or until the mussels are cooked. Before serving, sprinkle with chopped parsley.
Divide the fish stew between four plates. Carefully take the fish from the pot using a fish spatula or a spoon. Be careful because the fish is soft and can easily fall apart. Drizzle with olive oil and optionally serve with additional parsley and a lemon wedge.