MRI
MIAX

Mad River Investors’s Miami International Holdings MIAX Stock Holding History

Mad River Investors’s Portfolio MIAX Stock Details MIAX Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$10.7M Buy
289,000
+207,750
+256% +$9.29M 4.01% 6
2026
Q1 		$3.16M Buy
81,250
+6,200
+8% +$255K 1.14% 12
2025
Q4 		$3.33M Buy
75,050
+450
+0.6% +$20.1K 1.52% 13
2025
Q3 		$3M Buy
+74,600
New +$2.73M 1.28% 14

Other funds holding MIAX

HKAM
Horizon Kinetics Asset Management New York $8.82B AUM 23.05% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $153B AUM 38.14% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
Susquehanna International Group
Susquehanna International Group Bala Cynwyd, Pennsylvania $1.28T AUM 58.89% 1-Year Est. Return
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Invesco
Invesco Atlanta, Georgia $1.26T AUM 61.52% 1-Year Est. Return
JD6
J Digital 6 Chicago, Illinois $169M AUM 111.5% 1-Year Est. Return
William Blair & Company
William Blair & Company Chicago, Illinois $38.4B AUM 25.71% 1-Year Est. Return
Balyasny Asset Management
Balyasny Asset Management Chicago, Illinois $80.2B AUM 51.53% 1-Year Est. Return

Mad River Investors's MIAX Position: Q2 2026 in Review

Mad River Investors increased its Miami International Holdings (MIAX) stake by 256% in Q2 2026, buying an estimated $9.29M and bringing the position to 289,000 shares worth $10.7M. The position accounts for 4.01% of the portfolio, ranked #6.

Mad River Investors first reported a position in MIAX in Q3 2025 and has held it in 4 quarters since. 205 funds tracked by Wall St. Rank hold MIAX as of Q2 2026.

  • Mad River Investors held 289,000 shares of Miami International Holdings worth $10.7M as of Q2 2026.
  • Mad River Investors bought 207,750 Miami International Holdings shares in Q2 2026, an estimated $9.29M.
  • Miami International Holdings made up 4.01% of Mad River Investors's portfolio in Q2 2026, its #6 holding.
  • Mad River Investors first reported a position in Miami International Holdings in Q3 2025 and has held it in 4 quarters since.
  • 205 funds tracked by Wall St. Rank held Miami International Holdings as of Q2 2026.

Based on Mad River Investors's 13F filing for Q2 2026, filed 3 Aug 2026.