Portolan Capital Management, LLC MRX — MAREX GROUP PLC

Ownership history in Portolan Capital Management, LLC  ·  4 quarters on record

AI Ownership Summary

Portolan Capital Management, LLC reported MAREX GROUP PLC (MRX) in 4 quarterly 13F filings from 2024 Q4 through 2025 Q4. Peak portfolio weight reached 0.86% in 2025 Q4. The latest visible filing shows MRX at 0.86% of the fund.

This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings.

What this MRX ownership page tells you

This page is designed to answer the real investor question behind a 13F filing: how meaningful was Portolan Capital Management, LLC's position in MAREX GROUP PLC, and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.

Freshest filing
Latest Reported Filing
2025 Q4

MRX was reported at 0.86% of portfolio in the most recent visible filing.

High-water mark
Peak Conviction
0.86% in 2025 Q4

Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.

Time in book
Holding Window
2024 Q4 to 2025 Q4

Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.

Decision context
Why It Matters
Position size beats headlines

Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.

MRX stock page Portolan Capital Management, LLC fund profile Portolan Capital Management, LLC full holdings
How Portolan Capital Management, LLC held MRX — position size vs. price
% of Fund (quarterly)    MRX price (quarter-end, indexed to 100)    SPY (indexed to 100)    QQQ (indexed to 100)
📋 Quarterly Holdings History 4 quarters  ▾
Quarter Action Sold % After 3M Timing Shares Change Chg % % of Fund Mkt Value Filed Price (Filed)
2025 Q4 ADDED — — — 418,745 +334,986 +399.9% 0.86% $16.1M 2026-02-17 $41.58
2025 Q2 REDUCED 51.9% -13.3% ✅ 83,759 -90,437 -51.9% 0.21% $3.3M 2025-08-13 $35.07
2025 Q1 REDUCED 22.1% +12.2% ❌ 174,196 -49,418 -22.1% 0.47% $6.2M 2025-05-15 $45.58
2024 Q4 INITIATED — — — 223,614 — — 0.47% $7.0M 2025-02-13 $34.79

🏢 Other funds also holding MRX

As of 2026 Q1 — sorted by position size

Grandeur Peak Global Advisors, LLC 3Y 7Y 13.84% Praetorian PR LLC 3Y 8.11% Ophir Asset Management Pty Ltd 3Y 6.47% Deltroit Asset Management (UK) LLP 3.22% Engle Capital Management, L.P. 3Y 7Y 3.05% Granahan Investment Management, LLC 3Y 7Y 2.64% EPACRIA CAPITAL PARTNERS, LLC 3Y 2.26% GLOBEFLEX CAPITAL L P 3Y 7Y 1.43% SAMLYN CAPITAL, LLC 3Y 7Y 1.28% MOODY ALDRICH PARTNERS LLC 3Y 7Y 1.12%

FAQ About Portolan Capital Management, LLC and MRX

These are the practical questions this page is built to answer before you even open the full history table.

How long has Portolan Capital Management, LLC reported owning MRX?

Portolan Capital Management, LLC reported MRX across 4 quarterly 13F filings, from 2024 Q4 through 2025 Q4.

What was the largest reported MRX position in Portolan Capital Management, LLC's portfolio?

The largest reported portfolio weight for MRX was 0.86% in 2025 Q4.

What is the latest reported MRX position on this page?

The most recent filing on this page is 2025 Q4, when Portolan Capital Management, LLC reported 418,745 shares, equal to 0.86% of portfolio, with an estimated market value of $16.1M.

What does the chart on this MRX ownership page compare?

The chart compares Portolan Capital Management, LLC's quarterly MRX portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.

How well did Portolan Capital Management, LLC time their MRX position?

Based on 13F filing dates vs. subsequent MRX price moves, Portolan Capital Management, LLC correctly timed 2 out of 3 reported position changes (67%). The annualised alpha on MRX relative to SPY over the holding period was +5.4%.

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