At a price of C$0.15 a share, the shares were acquired for C$803,571.
Fortuna now owns 10.7mln shares of Prospero which represents 22.8% of issued and outstanding shares.
Shares were acquired by Fortuna for investment purposes, the company said.
Depending on market and other conditions, Fortuna may increase or decrease its ownership, control, or direction over Prospero's shares via market transactions, private agreements and otherwise, according to the company.
Shares of Fortuna were up 0.42% and closed at C$7.13 on Wednesday.