Assai debuted on Brazil's stock exchange at 73 reais per share, and with a market capitalization of 19.6 billion reais ($3.51 billion). The unit was spun off on Friday and was listed separately on Brazil's B3 exchange on Monday.
As the first quote for reference in the listing was the unit's book value, Assai stock opened up almost 400%.
Former parent GPA's shares were down 72% at 18.75 reais, and the company's market value dropped from 22.3 billion reais on Friday to 5 billion reais, as investors attributed most of the value to the wholesale unit.
Brazilian shoppers have embraced wholesale format stores in general given the relative value and range of products they offer, a trend that has also benefited rival Carrefour Brasil's Atacadao brand.
The combined value of Assai and GPA, controlled by France's Casino Guichard Perrachon, rose 10% to 24.6 billion reais on Monday from 22.3 billion reais on Friday.
According to traders, the wild swings in share prices in the first trading day happened because the reference used for Assai was book value. There was no bookbuilding for the listing of the unit.
($1 = 5.5823 reais)
(Reporting by Tatiana Bautzer and Paula Laier in Sao Paulo; Editing by Matthew Lewis)
By Tatiana Bautzer and Paula Laier