1. Preheat your grill to medium-high heat.
2. In a mixing bowl, combine olive oil, chili powder, cumin, garlic powder, salt, and black pepper. Coat the fish fillets with this mixture.
3. Grill the fish for about 3-4 minutes on each side, until it flakes easily with a fork.
4. In another bowl, mix shredded cabbage, shredded carrots, chopped cilantro, lime juice, olive oil, and salt to make the slaw.
5. Warm the corn tortillas on the grill for about 30 seconds on each side.
6. Assemble the tacos by placing grilled fish on each tortilla, topping with slaw, a dollop of sour cream, and a spoonful of salsa.