ASC files 13G: 6.4% stake; sole voting 16,112,823 FSM shares

Rhea-AI Filing Summary

Fortuna Mining Corp. (FSM) received a Schedule 13G from Arrowstreet Capital, Limited Partnership and Arrowstreet Capital Holding LLC reporting beneficial ownership of 19,677,691 Common Shares, representing 6.4% of the class as of 09/30/2025.

Arrowstreet reports sole voting power over 16,112,823 shares and sole dispositive power over 19,677,691 shares, with no shared voting or dispositive power. The securities are held by investment advisory clients of Arrowstreet Capital, and no single client is known to hold more than five percent of the class. The filers certify the shares were acquired and are held in the ordinary course and not for the purpose of changing or influencing control.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

FORTUNA MINING CORP.

(Name of Issuer)

Common Shares

(Title of Class of Securities)

349942102

(CUSIP Number)

09/30/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 349942102

1

Names of Reporting Persons

ARROWSTREET CAPITAL, LIMITED PARTNERSHIP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MASSACHUSETTS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 16,112,823.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 19,677,691.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

19,677,691.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.4 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No. 349942102

1

Names of Reporting Persons

ARROWSTREET CAPITAL HOLDING LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 16,112,823.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 19,677,691.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

19,677,691.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.4 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: FORTUNA MINING CORP.
(b)	Address of issuer's principal executive offices: 1111 MELVILLE STREET, SUITE 820, VANCOUVER, BRITISH COLUMBIA, CANADA, V6E 3V6.
Item 2.
(a)	Name of person filing: Arrowstreet Capital, Limited Partnership ("ASC") Arrowstreet Capital Holding LLC ("ACH")
(b)	Address or principal business office or, if none, residence: 200 Clarendon Street, 30th Floor Boston, MA 02116
(c)	Citizenship: ASC: Massachusetts ACH: Delaware
(d)	Title of class of securities: Common Shares
(e)	CUSIP No.: 349942102
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 19,677,691
(b)	Percent of class: ASC: 6.4% ACH: 6.4%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 16,112,823
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 19,677,691
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. This Schedule is filed by ASC, in its capacity as investment adviser to a number of its investment advisory clients, and by ACH, in its capacity as the ultimate parent company of ASC. The securities to which this Schedule relates are held by investment advisory clients of ASC. No such investment advisory client of ASC is known by ASC or by ACH to hold more than five percent of the class of securities to which this Schedule relates.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ARROWSTREET CAPITAL, LIMITED PARTNERSHIP

Signature:	Kimberly Kelley
Name/Title:	Chief Compliance Officer
Date:	11/13/2025

ARROWSTREET CAPITAL HOLDING LLC

Signature:	Eric Burnett
Name/Title:	Member and Authorized Signatory
Date:	11/13/2025

FAQ

What stake in FSM did Arrowstreet disclose in this Schedule 13G?

Arrowstreet reported beneficial ownership of 19,677,691 Common Shares, or 6.4% of Fortuna Mining Corp.'s class as of 09/30/2025.

How much voting and dispositive power did Arrowstreet report over FSM shares?

They reported sole voting power over 16,112,823 shares and sole dispositive power over 19,677,691 shares, with no shared power.

Who holds the reported FSM shares related to Arrowstreet's filing?

The shares are held by investment advisory clients of Arrowstreet Capital; no single client is known to hold more than five percent.

What type of filing is this for FSM and what does it indicate?

It is a Schedule 13G, indicating a passive beneficial ownership position acquired in the ordinary course.

What is the event date for Arrowstreet’s reported FSM ownership?

The date of the event requiring the filing is 09/30/2025.

Did the filers state any intent to influence control at Fortuna Mining?

They certified the securities were not acquired or held to change or influence control.