Chop the tomatoes and place in a bowl; ensure any tomato juice on the board or in the can goes along for the ride. Remove the sausage from its casing, pull the meat into small nuggets and set in a second bowl.
Heat the oil in medium-sized pot set over medium heat. Add the onion, garlic and chorizo and cook until the onions are tender and the sausage is cooked through, about 5 minutes. Add the wine, bay leaf and saffron and bring to a simmer. Simmer until the wine has reduced by half. Add the tomatoes, return to a simmer, and simmer 2 minutes more. Stir in the fish and simmer until cooked through, about 5 minutes. Spoon the stew into bowls, sprinkle with parsley and serve.
Note: Saffron threads are sold in bottles in the herb and spice aisle.