Put the vinegar, wine, peppercorns, sugar, allspice, and a pinch of salt in a sauce pot over medium heat. Bring to a simmer, stirring until the sugar dissolves. Add the carrot and onion and cook until crisp but tender, about 8 minutes. Remove from the heat, add the cucumber and put into a small bowl. Discard the peppercorns. Set aside until ready to use or refrigerate for 1 hour, if desired.
Heat the vegetable oil in a large skillet over medium-high heat.
Rinse the fish fillets and pat dry. Coat them in lime juice, season with salt and pepper and flour both sides. Carefully, add the fish, skin side down, to the skillet and fry until the bottom is golden and releases easily from the pan, about 3 minutes. Flip the fillets and sear until cooked through, about 2 to 3 minutes. Transfer the fish to a nonreactive serving platter. Serve warm or cold, pouring the pickled garnish over fish just before serving. If serving cold, refrigerate separately.