CASTLEARK MANAGEMENT LLC — 13F Holdings & Portfolio
CIK 1106832 · latest 13F-HR filed 2026-08-14
CASTLEARK MANAGEMENT LLC manages $3.71B in 13F-reported U.S. long-equity assets across 309 reported positions as of its 2026-06-30 13F-HR filing. Its largest disclosed positions are NVDA (7.01%), GOOGL (4.89%), AAPL (3.68%). Quarter over quarter (versus its 2026-03-31 filing) the fund opened 59 new positions and exited 42; 134 existing positions rose in reported value and 75 fell.
AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.
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AUM
$3.71B
Long-equity book
Holdings
309
Distinct positions
Period
2026-06-30
Filed 2026-08-14
Q/Q Activity
+59 / −42 / ↑134 / ↓75
vs 2026-03-31
Portfolio charts
Latest quarter's book, what changed, and how the portfolio has evolved across filings.
Portfolio map
Q2 26NVDA7.0% · +3%GOOGL4.9% · +21%AAPL3.7% · +35%LRCX3.3% · -16%MSFT2.9% · +11%LLY2.8% · +19%AVGO2.5% · +20%SPIB2.4% · 0%V2.2% · +54%ANET2.2% · +10%GOVT2.0% · 0%VMBS1.9% · 0%AMD1.9% · +34%GILD1.8% · +54%AMZN1.7% · +9%GEV1.5% · +11%META1.4% · -24%ADI1.3% · +55%MA1.3% · -1%MS1.2% · +781%SNOW1.1% · +23%VRT1.1% · +10%TPR1.0% · +30%SPTS1.0% · 0%VCLT0.9% · 0%NOW0.9% · +6%TLH0.7% · 0%BKNG0.7% · +2694%MCO0.7% · +216%TSLA0.5% · +23%CAT0.5% · +36%GE0.5% · +72%TSM0.5% · 0%LGND0.5% · +27%SN0.5% · newMBB0.5% · 0%TWLO0.5% · +245%BKR0.5% · -15%GTX0.5% · -4%JPM0.4% · 0%ASND0.4% · -9%JBHT0.4% · +150%FANG0.4% · -38%GM0.4% · +101%BTSG0.4% · -14%SMTC0.4% · -15%FCFS0.4% · -4%MAR0.4% · +354%IGIB0.4% · 0%TJX0.4% · 0%UBER0.4% · +12%UCTT0.4% · -4%NOVT0.4% · +138%AXON0.4% · +164%BA0.3% · +128%XBI0.3% · 0%ESI0.3% · -4%MYRG0.3% · +42%GH0.3% · -50%TLT0.3% · 0%
Box size = position value; colour = change in share count vs the prior quarter (green added, red trimmed, blue new). Rows split across managers or share classes are combined. Click a box for the stock.
Sector mix
% of 13F valueSectors from each company's SIC code; funds and ETFs grouped separately.
Biggest buys and sells
Q1 26 → Q2 26Estimated from the change in shares held × the quarter-end price, so price moves alone don't count as buying. New and exited positions are included.
13F assets and positions
4 quartersTotal reported 13F value (bars) and number of positions (line) each quarter. Value changes include market moves.
Top positions over time
reported valueThe eight largest current positions, valued at each quarter end.
Concentration
top 10 = 33.9%Cumulative share of the portfolio held in the largest N positions.
Firm Profile & Key People
As of the firm’s regulatory filing dated Apr 1, 2026.
Assets Under Management
$4.59B
Discretionary
$4.59B
Employees
28
Accounts
66
| Name | Title / Status | Ownership | Type |
|---|---|---|---|
| BAXTER, GREGORY, PETER Control | PORTFOLIO MANAGER since Jan 2013 | Less than 5% | Individual |
| BECKER, DANIEL, P Control | CO-CHIEF INVESTMENT OFFICER since May 2020 | Less than 5% | Individual |
| CASTELLINI, JAMES, H Control | CHIEF LEGAL OFFICER since Oct 2004 | Less than 5% | Individual |
| CASTELLINI, JEROME, A Control | CHIEF EXECUTIVE, CO-CHIEF INVESTMENT OFFICER since Jan 1999 | 50–75% | Individual |
| CASTLEARK HOLDINGS, LLC Control | HOLDING COMPANY since Mar 2021 | 75% or more | Domestic Entity |
| Hagan, Joseph, M Control | CO-PORTFOLIO MANAGER since Jan 2018 | Less than 5% | Individual |
| Johnson, Sarah, Williams Control | CHIEF COMPLIANCE OFFICER since Jan 2025 | Less than 5% | Individual |
| OSTROWSKI, QUENTIN, MICHAEL Control | CO-PORTFOLIO MANAGER since Jan 2013 | Less than 5% | Individual |
| REDDI, AJOY Control | PORTFOIO MANAGER since Jan 2018 | Less than 5% | Individual |
| STARK, JAMES, ARTHUR Control | CO-PORTFOLIO MANAGER since Jan 2013 | Less than 5% | Individual |
| BAXTER, GREGORY, PETER Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since Jan 2013 | General partner, trustee or manager | Individual |
| BECKER, DANIEL, P Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since May 2020 | General partner, trustee or manager | Individual |
| CASTELLINI, JEROME, A Control Indirect owner via CASTLEARK HOLDINGS, LLC | MANAGING MEMBER since Feb 1999 | 50–75% | Individual |
| Hagan, Joseph, M Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since Jan 2018 | General partner, trustee or manager | Individual |
| OSTROWSKI, QUENTIN, MICHAEL Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since Jan 2013 | General partner, trustee or manager | Individual |
| REDDI, AJOY Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since Jan 2018 | General partner, trustee or manager | Individual |
| STARK, JAMES, ARTHUR Control Indirect owner via CASTLEARK HOLDINGS, LLC | MEMBER since Jan 2013 | General partner, trustee or manager | Individual |
Ownership & leadership changes · 17 filings with changes since Feb 1, 2012
From the firm’s regulatory filings, newest first. Dates are filing dates: a filing that no longer lists someone does not say when they left.
Apr 1, 2026 filing
- ChangedBAXTER, GREGORY, PETER · title MEMBER, COMMON UNITS → PORTFOLIO MANAGER
- ChangedBAXTER, GREGORY, PETER · indirect via CASTLEARK HOLDINGS, LLC: title MEMBER, COMMON UNIT → MEMBER
- ChangedBECKER, DANIEL, P · indirect via CASTLEARK HOLDINGS, LLC: title CO-CHIEF INVESTMENT OFFICER → MEMBER
- ChangedCASTELLINI, JEROME, A · title MANAGING MEMBER, PREFERRED AND COMMON → CHIEF EXECUTIVE, CO-CHIEF INVESTMENT OFFICER
- ChangedHagan, Joseph, M · title MEMBER, PREFERRED AND COMMON → CO-PORTFOLIO MANAGER
- ChangedHagan, Joseph, M · indirect via CASTLEARK HOLDINGS, LLC: title MEMBER, PREFERRED AND COMMON → MEMBER
- ChangedOSTROWSKI, QUENTIN, MICHAEL · title MEMBER, COMMON UNITS → CO-PORTFOLIO MANAGER
- ChangedOSTROWSKI, QUENTIN, MICHAEL · indirect via CASTLEARK HOLDINGS, LLC: title MEMBER, COMMON UNITS → MEMBER
- ChangedREDDI, AJOY · title MEMBER, PREFERRED AND COMMON → PORTFOIO MANAGER
- ChangedREDDI, AJOY · indirect via CASTLEARK HOLDINGS, LLC: title MEMBER, PREFERRED AND COMMON → MEMBER
- ChangedSTARK, JAMES, ARTHUR · title MEMBER, COMMON UNITS → CO-PORTFOLIO MANAGER
- ChangedSTARK, JAMES, ARTHUR · indirect via CASTLEARK HOLDINGS, LLC: title MEMBER, COMMON UNITS → MEMBER
Aug 19, 2025 filing
- AddedBAXTER, GREGORY, PETER · MEMBER, COMMON UNIT · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedBECKER, DANIEL, P · CO-CHIEF INVESTMENT OFFICER · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedCASTELLINI, JEROME, A · MANAGING MEMBER · 50–75% · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedCASTLEARK HOLDINGS, LLC · HOLDING COMPANY · 75% or more · control person
- AddedHagan, Joseph, M · MEMBER, PREFERRED AND COMMON · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedOSTROWSKI, QUENTIN, MICHAEL · MEMBER, COMMON UNITS · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedREDDI, AJOY · MEMBER, PREFERRED AND COMMON · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
- AddedSTARK, JAMES, ARTHUR · MEMBER, COMMON UNITS · General partner, trustee or manager · indirect via CASTLEARK HOLDINGS, LLC · control person
Feb 3, 2025 filing
- No longer listedBRANCAZIO, CHRISTOPHER, JOHN · CHIEF COMPLIANCE OFFICER · Less than 5% · control person · listed since Jan 2024
- AddedJohnson, Sarah, Williams · CHIEF COMPLIANCE OFFICER · Less than 5% · control person
Mar 23, 2024 filing
- No longer listedTAKAZAWA, ROBERT, SATORU · MEMBER, PREFERRED AND COMMON · 5–10% · control person · listed since Jan 2000
Jan 22, 2024 filing
- No longer listedSIMEK, RICHARD, J · CHIEF COMPLIANCE OFFICER · Less than 5% · control person · listed since Sep 2012
- AddedBRANCAZIO, CHRISTOPHER, JOHN · CHIEF COMPLIANCE OFFICER · Less than 5% · control person
Mar 31, 2021 filing
- ChangedBECKER, DANIEL, P · title EXECUTIVE OFFICER → CO-CHIEF INVESTMENT OFFICER
Jun 8, 2020 filing
- No longer listedDOLSEN, KEVIN, M · MEMBER, PREFERRED AND COMMON · 10–25% · control person · listed since Apr 2014
- AddedBECKER, DANIEL, P · EXECUTIVE OFFICER · Less than 5% · control person
Apr 30, 2020 filing
- No longer listedROCKEY, JOAN, KATHRYN · MEMBER, PREFERRED AND COMMON · Less than 5% · control person · listed since Jan 2014
Mar 30, 2019 filing
- AddedBAXTER, GREGORY, PETER · MEMBER, COMMON UNITS · Less than 5% · control person
- AddedHagan, Joseph, M · MEMBER, PREFERRED AND COMMON · Less than 5% · control person
- AddedOSTROWSKI, QUENTIN, MICHAEL · MEMBER, COMMON UNITS · Less than 5% · control person
- AddedREDDI, AJOY · MEMBER, PREFERRED AND COMMON · Less than 5% · control person
- ChangedSTARK, JAMES, ARTHUR · title MEMBER, COMMON → MEMBER, COMMON UNITS
Apr 9, 2018 filing
- ChangedDOLSEN, KEVIN, M · ownership 5–10% → 10–25%
Older changes (8 more filings)
Apr 5, 2018 filing
- ChangedCASTELLINI, JEROME, A · ownership 75% or more → 50–75%
- ChangedDOLSEN, KEVIN, M · ownership Less than 5% → 5–10%
- ChangedTAKAZAWA, ROBERT, SATORU · ownership Less than 5% → 5–10%
Jul 20, 2017 filing
- ChangedCASTELLINI, JAMES, H · title GENERAL COUNSEL → CHIEF LEGAL OFFICER
- ChangedCASTELLINI, JEROME, A · title PRESIDENT → MANAGING MEMBER, PREFERRED AND COMMON
- ChangedDOLSEN, KEVIN, M · title CHEIF EXECUTIVE OFFICER → MEMBER, PREFERRED AND COMMON
- ChangedROCKEY, JOAN, KATHRYN · title CHEIF FINANCIAL OFFICER → MEMBER, PREFERRED AND COMMON
- ChangedSTARK, JAMES, ARTHUR · title SENIOR VICE PRESIDENT → MEMBER, COMMON
- ChangedTAKAZAWA, ROBERT, SATORU · title SENIOR VICE PRESIDENT → MEMBER, PREFERRED AND COMMON
Jun 12, 2017 filing
- AddedROCKEY, JOAN, KATHRYN · CHEIF FINANCIAL OFFICER · Less than 5% · control person
Jun 9, 2014 filing
- AddedDOLSEN, KEVIN, M · CHEIF EXECUTIVE OFFICER · Less than 5% · control person
Mar 31, 2014 filing
- No longer listedCLARK, EDWARD · VICE PRESIDENT & SECRETARY · Less than 5% · control person · listed since Jan 1999
- AddedSTARK, JAMES, ARTHUR · SENIOR VICE PRESIDENT · Less than 5% · control person
- ChangedTAKAZAWA, ROBERT, SATORU · title SENIOR VP → SENIOR VICE PRESIDENT
Apr 3, 2013 filing
- AddedSIMEK, RICHARD, J · CHIEF COMPLIANCE OFFICER · Less than 5% · control person
- AddedTAKAZAWA, ROBERT, SATORU · SENIOR VP · Less than 5% · control person
- ChangedCASTELLINI, JAMES, H · title CHIEF COMPLIANCE OFFICER → GENERAL COUNSEL
Apr 30, 2012 filing
- ChangedCASTELLINI, JEROME, A · ownership 25–50% → 75% or more
- ChangedCLARK, EDWARD · ownership 25–50% → Less than 5%
Feb 1, 2012 filing (earliest on record)
- ListedCASTELLINI, JAMES, H · CHIEF COMPLIANCE OFFICER · Less than 5% · control person
- ListedCASTELLINI, JEROME, A · PRESIDENT · 25–50% · control person
- ListedCLARK, EDWARD · VICE PRESIDENT & SECRETARY · 25–50% · control person
Quarter-over-quarter changes
Changes in reported position value vs the prior 13F, so price moves count too, not just shares bought or sold.
Top Adds (vs prior quarter)
- ALPHABET INC$61.0M +50.8%
- LAM RESEARCH CORP$51.0M +70.9%
- ADVANCED MICRO DEVICES INC$51.0M +281.6%
- APPLE INC$47.8M +53.8%
- NVIDIA CORPORATION$40.6M +18.5%
Top Trims
- SCHWAB CHARLES CORP-$46.5M -98.2%
- SHOPIFY INC-$26.9M -73.0%
- CHEVRON CORPORATION-$26.3M -93.0%
- META PLATFORMS INC-$18.1M -25.5%
- DIAMONDBACK ENERGY INC-$12.7M -44.4%
New Positions
- SHARKNINJA INC$19.4M
- ASCENDIS PHARMA A/S$16.5M
- HEXCEL CORP NEW$10.6M
- CROCS INC$10.4M
- SENSIENT TECHNOLOGIES CORP$10.2M
Exited Positions
- ULTA BEAUTY INC$26.5M
- ASCENDIS PHARMA A/S$15.5M
- FIVE BELOW INC$9.2M
- TUTOR PERINI CORP$9.0M
- HASBRO INC$8.9M
CASTLEARK MANAGEMENT LLC Holdings (2026-06-30)
Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).
| # | Issuer | Symbol | CUSIP | Value | Weight | Shares | Type |
|---|---|---|---|---|---|---|---|
| 1 | NVIDIA CORPORATION | NVDA | 67066G104 | $260.0M | 7.01% | 1,299,605 | SH |
| 2 | ALPHABET INC | GOOGL | 02079K305 | $181.2M | 4.89% | 507,093 | SH |
| 3 | APPLE INC | AAPL | 037833100 | $136.6M | 3.68% | 472,108 | SH |
| 4 | LAM RESEARCH CORP | LRCX | 512807306 | $123.0M | 3.32% | 283,808 | SH |
| 5 | MICROSOFT CORP | MSFT | 594918104 | $109.2M | 2.94% | 292,770 | SH |
| 6 | ELI LILLY & CO | LLY | 532457108 | $105.2M | 2.84% | 87,697 | SH |
| 7 | BROADCOM INC | AVGO | 11135F101 | $92.1M | 2.48% | 243,896 | SH |
| 8 | SPDR SERIES TRUST | SPIB | 78464A375 | $90.0M | 2.43% | 2,688,380 | SH |
| 9 | VISA INC | V | 92826C839 | $81.0M | 2.18% | 236,166 | SH |
| 10 | ARISTA NETWORKS INC | ANET | 040413205 | $80.4M | 2.17% | 473,319 | SH |
| 11 | ISHARES TR | GOVT | 46429B267 | $75.8M | 2.04% | 3,329,569 | SH |
| 12 | VANGUARD SCOTTSDALE FDS | VMBS | 92206C771 | $69.6M | 1.88% | 1,487,800 | SH |
| 13 | ADVANCED MICRO DEVICES INC | AMD | 007903107 | $69.0M | 1.86% | 118,865 | SH |
| 14 | GILEAD SCIENCES INC | GILD | 375558103 | $66.6M | 1.80% | 527,542 | SH |
| 15 | AMAZON COM INC | AMZN | 023135106 | $63.9M | 1.72% | 268,249 | SH |
| 16 | GE VERNOVA INC | GEV | 36828A101 | $54.2M | 1.46% | 46,101 | SH |
| 17 | META PLATFORMS INC | META | 30303M102 | $52.8M | 1.42% | 93,744 | SH |
| 18 | ANALOG DEVICES INC | ADI | 032654105 | $48.0M | 1.29% | 120,934 | SH |
| 19 | MASTERCARD INCORPORATED | MA | 57636Q104 | $47.0M | 1.27% | 91,462 | SH |
| 20 | MORGAN STANLEY | MS | 617446448 | $43.6M | 1.18% | 208,542 | SH |
| 21 | SNOWFLAKE INC | SNOW | 833445109 | $42.5M | 1.14% | 166,818 | SH |
| 22 | VERTIV HOLDINGS CO | VRT | 92537N108 | $41.5M | 1.12% | 123,901 | SH |
| 23 | TAPESTRY INC | TPR | 876030107 | $38.9M | 1.05% | 265,749 | SH |
| 24 | SPDR SERIES TRUST | SPTS | 78468R101 | $38.7M | 1.04% | 1,334,080 | SH |
| 25 | VANGUARD SCOTTSDALE FDS | VCLT | 92206C813 | $33.7M | 0.91% | 448,330 | SH |
| 26 | SERVICENOW INC | NOW | 81762P102 | $31.9M | 0.86% | 321,623 | SH |
| 27 | ISHARES TR | TLH | 464288653 | $25.9M | 0.70% | 258,432 | SH |
| 28 | BOOKING HOLDINGS INC | BKNG | 09857L108 | $24.4M | 0.66% | 136,776 | SH |
| 29 | MOODYS CORP | MCO | 615369105 | $24.2M | 0.65% | 53,444 | SH |
| 30 | TESLA INC | TSLA | 88160R101 | $20.2M | 0.55% | 48,070 | SH |
| 31 | CATERPILLAR INC | CAT | 149123101 | $20.2M | 0.54% | 18,980 | SH |
| 32 | GE AEROSPACE | GE | 369604301 | $19.7M | 0.53% | 52,830 | SH |
| 33 | TAIWAN SEMICONDUCTOR MANUFAC | TSM | 874039100 | $19.7M | 0.53% | 41,210 | SH |
| 34 | LIGAND PHARMACEUTICALS INC | LGND | 53220K504 | $19.6M | 0.53% | 62,043 | SH |
| 35 | SHARKNINJA INC | SN | G8068L108 | $19.4M | 0.52% | 127,170 | SH |
| 36 | ISHARES TR | MBB | 464288588 | $19.3M | 0.52% | 204,235 | SH |
| 37 | TWILIO INC | TWLO | 90138F102 | $19.1M | 0.51% | 92,390 | SH |
| 38 | BAKER HUGHES COMPANY | BKR | 05722G100 | $18.3M | 0.49% | 330,020 | SH |
| 39 | GARRETT MOTION INC | GTX | 366505105 | $17.0M | 0.46% | 469,470 | SH |
| 40 | JPMORGAN CHASE & CO | JPM | 46625H100 | $16.5M | 0.45% | 50,525 | SH |
| 41 | ASCENDIS PHARMA A/S | ASND | K08588103 | $16.5M | 0.44% | 61,696 | SH |
| 42 | HUNT J B TRANS SVCS INC | JBHT | 445658107 | $16.4M | 0.44% | 56,520 | SH |
| 43 | DIAMONDBACK ENERGY INC | FANG | 25278X109 | $15.9M | 0.43% | 90,680 | SH |
| 44 | GENERAL MTRS CO | GM | 37045V100 | $15.4M | 0.41% | 199,440 | SH |
| 45 | BRIGHTSPRING HEALTH SVCS INC | BTSG | 10950A106 | $14.8M | 0.40% | 212,430 | SH |
| 46 | SEMTECH CORP | SMTC | 816850101 | $14.8M | 0.40% | 91,218 | SH |
| 47 | FIRSTCASH HOLDINGS INC | FCFS | 33768G107 | $14.8M | 0.40% | 68,190 | SH |
| 48 | MARRIOTT INTL INC NEW | MAR | 571903202 | $14.0M | 0.38% | 37,910 | SH |
| 49 | ISHARES TR | IGIB | 464288638 | $13.8M | 0.37% | 259,994 | SH |
| 50 | TJX COS INC NEW | TJX | 872540109 | $13.7M | 0.37% | 90,620 | SH |
Filing History
| Period | Filed | AUM | Holdings | Accession |
|---|---|---|---|---|
| 2026-06-30 | 2026-08-14 | $3.71B | 309 | 0001106832-26-000004 |
| 2026-03-31 | 2026-05-15 | $3.02B | 292 | 0001106832-26-000003 |
| 2025-12-31 | 2026-02-13 | $3.41B | 294 | 0001106832-26-000001 |
| 2025-09-30 | 2025-11-17 | $3.57B | 284 | 0001106832-25-000008 |
Filer Information
Address
1 N WACKER DRSTE 3950
CHICAGO, IL 60606
Phone
(312) 456-9682
Filing Manager
CASTLEARK MANAGEMENT LLC
CHICAGO, IL
Signatory
James Castellini
Chief Legal Officer