Heat the oil in a large skillet over medium heat.
Season the salmon with ½ teaspoon salt and ¼ teaspoon pepper and cook until opaque throughout, 5 to 6 minutes per side.
Using a fork, flake the salmon into pieces.
Dividing the ingredients evenly, top the tostada shells with the salmon, black beans, corn, lettuce, and salsa. Serve with the lime wedges.