1. In a bowl, whisk beer, flour, and salt, blending well.
2. Rinse fish and pat dry. Cut into 10 equal pieces.
3. In a deep 5- to 6-quart pan, heat 1 inch salad oil to 360°. Using a fork, coat fish pieces with beer batter and lift out, draining briefly. Slide coated fish into oil, about 5 pieces at a time. Adjust heat to maintain oil temperature. When fritters are golden, in about 2 minutes, lift out with a slotted spoon and drain briefly on paper towels; keep warm. Repeat to fry remaining fish.
4. To assemble each taco, stack 2 tortillas; add a fish fritter, cabbage, mayonnaise, and salsa. Squeeze lime over filling, fold tortillas, and eat.
*Check fish for bones before cooking. Press surface with your fingers to locate; pull out with tweezers.