Preheat oven to 180°C. Bake fish for 20 minutes or until cooked through.
Place avocado in a bowl, squeeze in lime to taste and set aside. Cook corn kernels in a non-stick frying pan until brown and set aside. Combine onion, tomato and coriander in a bowl. Season with pepper.
To assemble tacos, slice and place fish fillets, avocado and a scoop of tomato salsa into each lettuce cup. Squeeze with extra lime juice and serve with additional side salad. Season with Sriracha if desired.