Pat fish dry and combine in a nonreactive bowl with the white wine, lime juice and garlic. Set aside to marinate about 10 to 15 minutes.
When fish is ready, remove it from the marinade, pat dry, and season with salt and freshly ground black pepper.
Heat oil in a large nonstick frying pan over medium-high heat. When oil shimmers, place fish skin-side down in skillet. Cook until opaque and firm to touch, about 3 minutes per side.
Flake the fish, squeeze one of the lime wedges over the top, and toss to coat. To make a taco, stack 2 tortillas on top of each other and fill with fish, lettuce, salsa, a few avocado slices, and a dollop of sour cream. Repeat to make 6 tacos total.