Heat oil in medium saucepan over medium heat until shimmering. Add chorizo, onion, and fennel and cook until vegetables are softened, about 8 minutes. Stir in garlic and cook until fragrant, about 30 seconds. Stir in wine, scraping up any browned bits. Stir in tomatoes with their juice and clam juice, bring to simmer, and cook until flavors meld, about 10 minutes.
Season cod with salt and pepper. Nestle cod into stew mixture, spoon some sauce over fillets, and bring to simmer. Reduce heat to medium-low, cover, and simmer until cod flakes apart when gently prodded with paring knife and registers 140 degrees, about 5 minutes. Gently stir in parsley and season with salt and pepper to taste. Drizzle individual portions with extra oil before serving.
