Arrowstreet discloses 15.1M shares in Fortuna Mining (FSM)

Rhea-AI Filing Summary

Fortuna Mining Corp ownership disclosure: Arrowstreet Capital, Limited Partnership and Arrowstreet Capital Holding LLC report beneficial ownership of 15,116,413 common shares, representing 5.0% of the class. The filing states these shares are held by investment advisory clients of Arrowstreet and ACH is the ultimate parent.

The Schedule 13G/A amendment lists 12,433,039 shares as sole voting power and 15,116,413 shares as sole dispositive power. Signatures are dated 05/15/2026.

Insights

Institutional Ownership Analyst

Large passive stake disclosed by Arrowstreet entities at the 5% threshold.

Arrowstreet reports 15,116,413 shares or 5.0% beneficial ownership in Fortuna Mining Corp. The filing identifies the holdings as managed for investment advisory clients, indicating passive investment reporting under Schedule 13G/A conventions.

Future filings may show changes in voting or disposition if client mandates change; the disclosed 12,433,039 sole voting shares and dispositive counts anchor the current position.

Compliance Counsel

Amendment clarifies ownership and attribution through parent and adviser entities.

The Schedule 13G/A is filed by Arrowstreet Capital, Limited Partnership as adviser and Arrowstreet Capital Holding LLC as ultimate parent, stating the securities are held by advisory clients. The filing follows disclosure rules for passive investors crossing the 5% reporting threshold.

Signatures by the Chief Compliance Officer and an authorized member dated 05/15/2026 complete the amendment; the filing preserves the adviser‑client attribution language required by Item 6.

Key Figures

Beneficial ownership: 15,116,413 shares Percent of class: 5.0% Sole voting power: 12,433,039 shares +2 more

5 metrics

Beneficial ownership 15,116,413 shares Beneficially owned as reported in Item 4

Percent of class 5.0% Percent of common shares reported

Sole voting power 12,433,039 shares Sole power to vote or to direct the vote

Filing type Schedule 13G/A Amendment disclosing passive ownership

Signature date 05/15/2026 Dates on authorized signatories

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power, investment advisory clients

4 terms

Schedule 13G/A regulatory

"This Schedule is filed by ASC, in its capacity as investment adviser"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned financial

"Amount beneficially owned: 15,116,413"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 15,116,413"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

investment advisory clients other

"securities to which this Schedule relate are held by investment advisory clients"

FAQ

What stake does Arrowstreet report in Fortuna Mining Corp (FSM)?

Arrowstreet reports beneficial ownership of 15,116,413 shares, equal to 5.0% of Fortuna Mining Corp's common shares. The filing attributes these holdings to Arrowstreet's investment advisory clients and names Arrowstreet Capital Holding LLC as the ultimate parent.

How many shares does Arrowstreet have sole voting power over in FSM?

Arrowstreet reports sole voting power over 12,433,039 shares of Fortuna Mining Corp common stock. The Schedule 13G/A shows zero shared voting power and ties voting power counts to the adviser entity.

Are these Arrowstreet holdings direct or held for clients of FSM?

The filing states the securities are held by Arrowstreet's investment advisory clients, not directly by the filer. Arrowstreet files in its capacity as adviser and Arrowstreet Capital Holding LLC as the ultimate parent company.

When was the amended Schedule 13G/A for FSM signed?

The amendment is signed and dated 05/15/2026 by Kimberly Kelley, Chief Compliance Officer, and Eric Burnett, Member and Authorized Signatory, completing the disclosure required at the 5% ownership threshold.

Does the filing indicate any client holds more than 5% of FSM?

No; the filing states that no investment advisory client known to Arrowstreet or ACH holds more than 5% of the class. Holdings are aggregated across advisory clients for reporting purposes.

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Accepted by SEC EDGAR 05/15/2026 - 11:39 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Fortuna Mining Corp

(Name of Issuer)

Common Shares

(Title of Class of Securities)

349942102

(CUSIP Number)

03/31/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 12,433,039.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 15,116,413.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

15,116,413.00

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)

5.0 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP Number(s): 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 12,433,039.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 15,116,413.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

15,116,413.00

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)

5 %

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, V6E 3V6, Canada
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, Boston, Massachusetts, 02116, United States
(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: 15,116,413
(b)	Percent of class: ASC: 5.0% ACH: 5.0%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 12,433,039
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 15,116,413
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	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 relate are held by investment advisory clients of ASC. The securities to which this Schedule relates are held by investment advisor 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:	05/15/2026

Arrowstreet Capital Holding LLC

Signature:	Eric Burnett
Name/Title:	Member and Authorized Signatory
Date:	05/15/2026