Baja Battered Fish

3/4 cup beer, preferably lager or pilsner
1/2 cup all-purpose flour
1/4 cup whole-wheat pastry flour
1/2 teaspoon salt
1/4 teaspoon dried oregano
1/4 teaspoon dry mustard
1/4 teaspoon cayenne pepper
1/4 teaspoon freshly ground pepper
1 pound tilapia or other firm white fish, sliced into 1/2-inch-by-2-inch strips
3 tablespoons canola oil, divided

Place beer, all-purpose flour, whole-wheat flour, salt, oregano, mustard, cayenne and pepper in a blender; blend until smooth, scraping down the sides as necessary. Transfer the batter to a shallow baking dish. Add fish, turning to coat all sides.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Transfer one-third of the battered fish to the pan, placing each piece into a little oil. Cook until golden brown, 3 to 4 minutes per side. Transfer cooked fish to a plate; keep warm. Add 1 tablespoon oil and half the remaining fish to the pan; cook as directed above, reducing the heat if necessary. Cook the remaining fish with the remaining 1 tablespoon oil. Serve immediately.