For batter, in a medium bowl, combine water and wine. Whisk in the 1 cup flour, the baking powder, and salt until mixture is smooth.
Rinse walleye fillets and pat dry with paper towels. Halve fillets crosswise, if you like. Coat fillets lightly with the 1/4 cup flour; dip into the prepared batter.
Fry fillets (1 large or 2 halves at a time) in a large skillet in 1/2 inch of deep hot oil (365 degree F) for 3 to 5 minutes or until golden and fish flakes easily with a fork, turning carefully once. Remove from oil; drain on paper towels. Keep warm while frying the remaining pieces.
Serve on buns with lettuce and tartar sauce. Makes 4 servings.