1. In a small bowl, mix together chili powder, cumin, garlic powder, and salt. Rub the spice mixture over the fish fillets.
2. Heat olive oil in a skillet over medium-high heat. Cook the fish for 3-4 minutes on each side, until it flakes easily with a fork. Remove from heat and set aside.
3. In a mixing bowl, combine mango, red onion, jalapeño, cilantro, lime juice, and salt. Mix well to make the salsa.
4. Warm the corn tortillas in a dry skillet or microwave.
5. Assemble the tacos by placing some fish on each tortilla, topping with mango salsa, shredded cabbage, and a dollop of sour cream. Serve with lime wedges.