1. Put at least 1/2 inch oil in cast-iron skillet. Over medium-high heat, bring oil to 350 degrees. (A drop of batter will sizzle energetically but not violently at this temperature.) 2. Meanwhile combine ginger, cayenne, paprika, salt, pepper and flour in a bowl. Beat egg with lime juice and about 1/4 cup cold water; stir into mixture, and stir in as much water as necessary to achieve consistency of pancake batter. Stir in fish. 3. When oil is heated, gently slide a few pieces of fish into it; do not crowd. Fry, turning once, until fish is crisp and golden brown all over, about 5 minutes. Repeat with rest of fish as necessary. Drain on paper towels, and serve immediately with lime wedges.