CASTLEARK MANAGEMENT LLC
SEC Form 13F institutional filer · CIK 0001106832
13F-HR · 115 reported holdings · 2026-03-31
SEC-registered institutional investment manager.
Reported long-US-equity value
$1.85B
Top-10 concentration
50.2%
CASTLEARK MANAGEMENT LLC — $1.85B AUM allocation strategy
CASTLEARK MANAGEMENT LLC files SEC Form 13F and reports $1.85B of long US equity value across 115 reported holdings for 2026-03-31.
Its largest sector bet is Information Technology 33.8%, followed by Communication Services 10.4% and Financials 7.6%.
The top 10 holdings account for 50% of reported value — a conviction-weighted book concentrated in its best ideas. The sector and industry splits below are of the same reported value. Track quarter-over-quarter adds, trims, new positions and exits below — sourced from SEC 13F filings, public domain.
CASTLEARK MANAGEMENT LLC — latest SEC 13F insights
Reported long-US-equity value (13F AUM)
$1.85B
total across 115 reported holdings · 2026-03-31 · excludes shorts, cash, non-US
Top-10 concentration
50% of value
higher = narrower conviction; lower = spread / hedging
Biggest adds (shares)
+$BKR +334K sh · +$21.2M+$FAST +142K sh · +$6.62M+$CMI +119K sh · +$6.78M
Biggest trims (shares)
−$BX −602K sh · −$45.2M−$MCHP −311K sh · −$19.6M−$AMZN −226K sh · −$57.8M
Exited to nil (held last quarter, gone now)
$PODD ($23M last qtr)$DAL ($18.1M last qtr)$COF ($7.98M last qtr)$DG ($6.89M last qtr)$T ($2.49M last qtr)
Sector allocation (share of reported value)
each slice is a share of the reported long-US-equity value — smaller sectors and the rest of the book roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Industry allocation (share of reported value)
- Semiconductors15.3%—
- Interactive Media & Services10.4%—
- Systems Software7.0%—
- Transaction & Payment Processing Services5.0%—
- Technology Hardware, Storage & Peripherals4.8%—
- Semiconductor Materials & Equipment3.9%—
- Pharmaceuticals3.6%—
- Communications Equipment2.9%—
- Other holdings47.2%—
the finer GICS cut of the same book — same denominator — smaller industries roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Top S&P 500 holdings
9 of 9 rows · sorted by Value ↓
| Ticker | Holding | Shares | Value | Δ QoQ | Weight |
|---|---|---|---|---|---|
| $NVDA | NVIDIA Corporation | 1.26M | $219M | -150K | 11.9% |
| $GOOG | Alphabet Inc. Class C Capital Stock | 418K | $120M | +36.4K | 6.5% |
| $MSFT | Microsoft Corporation | 264K | $97.8M | -105K | 5.3% |
| $AAPL | Apple Inc | 350K | $88.8M | -37K | 4.8% |
| $LRCX | Lam Research Corporation | 337K | $71.9M | -36.1K | 3.9% |
| $META | Meta Platforms Inc | 124K | $70.9M | +1.55K | 3.8% |
| $LLY | Eli Lilly and Company | 73.5K | $67.6M | -8.1K | 3.7% |
| $AVGO | Broadcom Inc | 203K | $62.7M | -3.18K | 3.4% |
| $ANET | Arista Networks Inc | 431K | $52.9M | +19.7K | 2.9% |
…and 106 more holdings in the full 13F filing (top positions only shown).
SEC Form 13F data sets · public domain · 45-day filing lag · >$100M AUM managers · as reported
← All 13F filers·← QuantOrb.pro
How to read Δ QoQ — the five insight categories, and the caveats
The categories. Analysts, quants and retail traders look past total portfolio value to isolate actionable signals. Five categories matter.
Conviction & concentration shifts
New positions vs complete exits — a brand-new stock signals high conviction; a full liquidation suggests a broken thesis or tax-loss harvesting. Aggressive sizing — look at share count, not dollars: a 20% share increase during a drawdown is strong dip-buying. Concentration — a narrowing top-5/10 means conviction; spreading capital across more names means hedging.
Sector & macro allocation rotations
Aggregating Δ QoQ moves across sectors shows where smart money is leaning in or sneaking out — rotating out of growth into defensives or energy, for example. The fund's total long equity exposure quarter-over-quarter is a proxy for overall institutional risk appetite.
Crowding & smart-money consensus
When several managers initiate or expand the same stock in the same quarter, that is institutional consensus. Contrarian reads: top pickers buying hard into a beaten-down name the market is selling.
Derivative & option overlays
Reported call/put changes indicate whether managers are adding downside hedges or leveraging upside exposure. Note: a long increase may be half of a market-neutral pair trade.
Who reads this
| Retail "cloners" | High-conviction ideas to replicate ~45 days after quarter-end. |
| Corporate IR | Which funds bought or dumped the stock, before the next call. |
| Quant / algo traders | Cross-sectional factor inputs: flow, momentum, ownership. |
Four caveats before you trade on it
- 45-day lag — holdings are quarter-end; positions may already be closed.
- Long-only — 13Fs miss shorts, pair trades and cash.
- No non-US / fixed income — the picture is US equities plus options.
- Corporate actions — splits and spinoffs distort raw share deltas.
Newsletter signup
Free subscription. Daily trading day morning dispatch. No spam.