Preheat the oven to 425 degrees F. Place the halibut in a non-stick or parchment-lined baking dish. Drizzle with the olive oil and lime juice; sprinkle with spices and herbs. Bake 12 to 15 minutes, or until just cooked through. Remove from the oven and cool slightly. While this occurs, heat the taco shells in the oven a few minutes. Coarsely flake the fish. Stuff the taco shells with lettuce, avocado, salsa, flaked fish and serve.