Season fish slices with adequate salt and pepper, then sprinkle lightly with tapioca flour to coat both sides.
Heat oil in a wok and deep-fry fish slices until golden brown. Dish out and place on a serving platter. Add ginger shreds to the remaining hot oil and fry until golden brown and crispy. Remove and drain on absorbent kitchen paper.
Combine sour plum sauce, lemon juice, sugar, fish sauce, sesame oil and bird´s eye chillies in a small bowl. Stir to mix until sugar is dissolved. Adjust taste; if too sour, add a little more sugar.
Pour sauce over the fish and sprinkle some mango and carrot shreds over. Top with the crispy ginger. Serve immediately.