Arrowstreet Capital Increases Stake in Fortuna Mining Corp to 5.0%

Arrowstreet Capital, Limited Partnership ("ASC") and Arrowstreet Capital Holding LLC ("ACH") filed a Schedule 13G/A on May 15, 2026, disclosing a 5.0% ownership stake in Fortuna Mining Corp (FSM). The filing indicates that ASC, acting as an investment adviser, and ACH, as its ultimate parent company, beneficially own 15,116,413 common shares. This represents a significant increase from their previously reported 0.0% position, crossing the 5% ownership threshold. Of the total shares held, Arrowstreet Capital maintains sole voting power over 12,433,039 shares and sole dispositive power over all 15,116,413 shares. The filing specifies that the securities are held by investment advisory clients of ASC, and no single client is known to hold more than 5% of the class. The acquisition was made in the ordinary course of business and not for the purpose of changing or influencing the control of the issuer. The event triggering this filing occurred on March 31, 2026.