Rub the black sea bass inside and out with a piece of ginger. Fill the cavity with the 2 pieces of ginger and 1 whole scallion. Place the fish into a ceramic baking dish that is just large enough to hold the fish yet able to fit into a wok. Sprinkle the salt over the fish, wrap with plastic wrap, and refrigerate until ready to cook. Cut the remaining 2 scallions into 1-inch lengths and julienne them.

Place a rack in the bottom of a wok. Pour in 4 cups of water and bring to a boil. When the water boils, place the baking dish with the fish on the rack. Sprinkle the fermented black beans over the fish, cover the wok, and allow the fish to steam for 10 minutes.

Remove the dish and the rack from the wok, pour out the water, and dry the wok completely. Return the wok to the burner.

Remove the ginger and scallion from the cavity of the fish and discard; reserve the cooking juices. Place the fish on a serving dish.

Heat the wok over high heat, then add oil. When the oil is hot, add the black vinegar, shredded ginger, julienne scallions, and the reserved cooking juices. Toss for 30 seconds, remove from the heat, and pour over the whole fish. Serve immediately.