Heat oil in a large skillet over medium heat. Sprinkle fish with taco seasoning and cook for 4 minutes on each side, breaking into large chunks as it cooks and becomes more flaky.
Meanwhile, dice mango and onion. Chop the cilantro and shred cabbage.
Combine mango, onion, cilantro, salt, pepper, and juice of half the lime. Slice remaining half of lime into wedges and set aside.
Top tortillas with cabbage, fish, and mango salsa. Spritz with remaining lime if desired. Serve immediately. (Servings size: 1-2 tacos filled with 2 ounces mahi and 1/3 cup toppings)