Heat the olive oil in a large pot over medium heat. Add the onion, garlic, and jalapeño. Cook for 3 minutes until the onion softens.
Stir in the chili powder and cumin. Cook for 30 seconds until the spices smell fragrant.
Pour in the diced tomatoes and fish stock. Bring the mixture to a simmer and cook for 5 minutes.
Add the haddock pieces to the pot. Simmer gently for 4 minutes.
Add the shrimp and cook for another 3 minutes until the shrimp turn pink and the haddock flakes easily.
Remove the pot from the heat. Stir in the lime juice and season with salt and black pepper to taste.
Ladle the stew into bowls and top each serving with chopped cilantro. Serve with lime wedges on the side.