Rinse the fish fillets under cold water and pat them dry with paper towels. In a small bowl, mix together the cumin, paprika, salt, and pepper. Rub the spice mixture evenly over the fish fillets.
Heat the olive oil in a large skillet over medium heat. Once hot, add the fish fillets and cook for about 3-4 minutes per side, or until the fish is cooked through and flakes easily with a fork. Remove from heat and let rest for a minute.
While the fish is cooking, prepare the mango salsa. In a medium bowl, combine the diced mango, red onion, jalapeño, cilantro, and lime juice. Stir gently to mix, and season with salt to taste.
In a separate dry skillet, warm the corn tortillas over medium heat for about 30 seconds on each side until they are pliable and slightly toasted.
Flake the cooked fish into large pieces and distribute among the warm tortillas. Top with a generous scoop of mango salsa and arrange avocado slices on top. If desired, add a handful of shredded cabbage for extra crunch.
Serve the tacos warm with additional lime wedges on the side for squeezing over the top.
Notes
For less heat, remove the seeds from the jalapeño.