Cut the fish into 1-inch strips, sprinkle with 1 teaspoon salt.
In a medium bowl stir together the buttermilk and beer. Add the fish to the bowl, making sure all fish is submerged. Allow to sit for ten minutes while you prep the dredge.
In a separate bowl stir together the cornmeal, flour, creole seasoning, and remaining ½ teaspoon salt.
Add 3 to 4 inches of oil in a pot. Clip a deep fry thermometer onto the side. Heat the oil to 350F, adjusting heat to maintain that temperature.
A few at a time, remove the fish strips from the buttermilk, allowing the excess to drip off. Add fish to the cornmeal dredge, tossing until well coated. Add to the oil, frying until golden, about 4 minutes. Remove from oil and allow to drain on a wire rack.
In a small bowl stir together the sour cream, and sriracha.
Spread the sour cream on the insides of the sliced baguette. Fill with a few pieces of fish, arugula and sliced tomato. Serve immediately.