Mix mayonnaise, capers, lemon juice and pepper sauce in bowl. Cover; refrigerate.
Pulse catfish in food processor until coarsely chopped. Mix cornmeal, crumbs and 1/4 teaspoon salt in small bowl. Add 1/2 cup cornmeal mixture to catfish in processor; reserve remainder for coating. Add red pepper, scallions, Cajun seasoning, black pepper, lemon juice, egg white and remaining 1/2 teaspoon salt to processor. Pulse until evenly combined, about 30 seconds.
Shape mixture into eighteen 2-inch patties, 2 tablespoons each. Coat in remaining cornmeal mixture.
Heat oil in large nonstick skillet over medium heat. Without crowding, cook cakes in batches 3 minutes, until light golden. Flip over; cook 3 minutes. Serve warm with remoulade.